Hey math friends! If you’re enjoying this video, could you double-check that you’ve liked it and subscribed to the channel? It’s a simple equation: your support + my passion = more great content! Thanks for helping me keep this going - you’re the best!
I'm thinking there is a more direct way. The glasses slide into the one below it somewhat, So each glass can be looked at as the "lower" part of the glass, and the "upper" part of the glass. So the 29cm stack on the left is made up of FIVE glass "uppers" and ONE glass "lowers". Let X = the "lower" part of the glass, which leads to the formula X+5y=29cm. The 17cm right stack is x+2y=17cm. using subtraction, the X's cancel out and you are left with 3y=12. Making y=4. Substituting that into either earlier formula (x+5y=29 or x+2y=17) gives x=9. So "lower" glass 9, plus higher glass 4, =13
A lot of commenters clearly already knew how to solve this problem. The video clearly and concisely explains how to solve it for someone who did not already know.
Both ways are great, and each can be used to cross-check the answer from the other. My own first inclination is the math approach, so it was good to see how to do it graphically, too. I love your videos, Susanne, because you have a talent for simplifying without oversimplifying. Mind Your Decisions!
Great Suzanna. I am 73 and you are bringing back my math skills. Please keep it going - appreciated and you are gorgeous as well. I wish I had during school a maths teacher as you - thanks.
Amazing, I could figure out the answer using method 2 myself. Also, loved how you applied simultaneous equations in method 1. Thanks for piquing my interest in maths after 2 long decades in school.
I like your puzzles , they take me back 60 years to my maths lessons , which I enjoyed tremendously . I solved this slightly differently ( in my head ) by multiply the short stack by 4 = 68 , subtracting the tall stack ( 4 tops + 1 glass ) = 39 = height of 3 glasses so divide by 3 = 13 .
i remember from my school days that the hardest part of this type of problem for many was describing it as a solvable formula, and where/how to assign the variables and that's where many schoolmates fell down at the first hurdle. If you have a 'math's brain' it's relatively straight forward, and 50+ years later, although i was a grade A maths student then, it takes a little more thinking about now, but still a great process and satisfaction when you solve it. so thanks.
My brain went to Method 1 as soon as I saw the image, because, in math, I'm usually thinking "how can I make an equation out of this?" However, Method 2 makes total sense! Love it!
Here's my working it out: Let a equal the segment of the glass height that doesn't stack. Let b equal the remaining glass height. 29 = 5a + b, 17 = 2a + b 29 - 5a = b = 17 - 2a 12 = 3a, a = 4 b = 17 - 2(4) = 17 - 8 = 9 ans: a + b = 4 + 9 = 13
I used the second method, and came up with 13 cm, just as you did. You can take this problem one step further and determine how much of each of the top four glasses is covered up by the one below it. Namely, if each glass is 13 cm, and 4 cm is exposed, then 9 cm of each glass (13-4) is hidden within the glass below it.
I think 13. Missing value = X Height of 1 added glass = Y 1. x + y = 17 2. x + 4y = 29 We can subtract "x + y" from "x + 4y" on the left, then 17 from 29 on the right to give us 3y (12) and y (4). Then we subtract y from "x + y" to get the answer: 17 - 4 = 13.
I instinctively used method 2, probably because it has been too long since I had to use ,method 1 in daily life. But it is nice to be reminded of method one, because that is more broadly applicable.
x + 4y = 29, x + y = 17. Solving the system of equations gives x = 13 and y = 4. I solved this sitting in my recliner w/o pencil and paper (~30 seconds). Now, I’ll watch your video. Your presentations are usually terrific.
They are basically the same method, only the second time it is applied graphically which is very good to explain how the elimination method work when solving a system of equations. In both case we subtract the second equation x+y=17 to the first one x+4y=29 e and we get 3y = 12
I used the graphical method and solved the problem in a few seconds. I simply used 29-17=12. Then I divided 12 by 3 to get 4. Then 17-4=13. It was interesting to see the formulaic approach also, which if I'm honest made this simple problem more complicated. I think this puzzle nicely shows that sometimes diving into maths is not necessary, and other times it is the only way to get an answer.
The two methods are kind of the same. When you subtracted one height from the other, it's the same as subtracting one equation from the other. And when you divided 12 by 3, it's like dividing both sides by three. And then, the final substitution to find the height of the glass.
Yes, the underlying math is the same. However, it is a very different way to approach the problem. I used the first method to find the results, then confirmed using the second method.
Yes, but it's a different way of thinking about the same thing. That's one of the things I love about maths, that there are so often very different angles to look at fundamentally the same thing
A tip that’s worked well for me teaching math to people who aren’t super comfortable with it. Use different variables, ones that will help them visualize it better. Math people are fine and prefer X and Y, but I’ve found normal people don’t internalize that well. So something like G for the glass, and T for the top. That way they can better think of it in a way that’s simpler to them.
@MathQueenSusanne I remember my calculus teacher, sometimes avoided using letters, used a "blob" instead. Especially with more complicated problems, to represent parts of expressions. Basically to communicate that the name didn't matter,
I did it in my head along the lines of the second method: the difference between the two stacks is the taller one has 3 more glasses so I worked out that those 3 glasses added 12 cm to the stack so each glass must add only 4cm to the stack which meant that the height of a glass is 17-4=13. The reason being, the pictures side by side made it very easy to break the stack of 5 glasses into 2 glasses (identical to the nearby stack of 2) and the additional 3.
And I did it a bit differently. I set t=the top of the glasses, and b=the rest of the glass. So I had 5t+b=29, and also 2t+b=17. After solving, the answer will be = t + b.
I used a variation of method 1. A assumed that the hight of a glass is X and that there is a stacking height that allows 2 glassed to be stacked in 2X -Y cm. Using this for stack 1: 5X - 4Y = 29 stack 2: 2X - Y = 17 Multiple (2) by 4 and we get: 8X - 4Y = 17 x 4 Subtract stack 1 from this to get: 3X = (17 x 4) -29 = 39 Divide by three to get X = 13cm
I used method two to solve it in my head in about 5 seconds. Interestingly, method 2 is basically the same as method 1, just more intuitively and less symbolic.
I did it in my head in less than 10 seconds. How? On the left we have FOUR of the glasses which are protruding outside of another one. On the left hand, we have ONE protruding. The difference is THREE. and 29-17 is 12. 12 is for four minus one protruding glasses so 1 is 4 cm. 17-4 is 13. Thanks.
The difference between the stack on the right and the stack in the middle is three glass tops. It's also 12cm taller. So each glass top = 12/3 (ie 4). So if we take that glass top off the centre stack, it will leave us with (17-4) 13cm for an empty glass. And that's our answer.
I used a math approach similar to the author's second method. Substitution: I wrote 17+3y=29 -> 3y =12 -> y=4, therefore x=13. And I checked my work, my brain is almost 70 years old.
I used the equation method - however I subtracted the smaller value from the larger a+4b=29 a+b=17 subtractubg the two you are left with 3b=12 therefore b = 12/3 = 4 a=17-4 =13 Whilst doing subtracting the larger equation from the smaller still gives the same answer, for me it's not as clean to end up with negative numbers when you don't need to.
As you said graphical, that triggered graph in my mind. Thus, you have two points (1,17) and (4,29) which generates the equation y = 4x + 13. The y intercept is the height of the glass and the slope the amount sticking out of the stacked glass.
The difference in height between the two stacks is 12cm. The difference in stack size is 3 cups. Division tells us that each stacked cup adds 4cm of height. 17 - 4 = 13 or 29 - (4*4) = 13
My way of solution ▶ The height of the glasses: x The height of each glass when placed inside the other: y ⇒ x+4y= 29 cm x+y= 17 cm ⇒ x+4y= 29 -x-y= -17 ⇒ 3y= 12 y= 4 cm x+4y= 29 y= 4 ⇒ x= 13 cm ✅
I'm an engineer and we often check our answers visually. If you take the 17 cm tall set of 2 glasses and place them on top of the one glass in the 29 cm tall glasses, you'll see that the 17 cm does not quite reach the top of the 29 cm. There are 4 glass segments in that area, and each was calculated as 4 cm, meaning the entire section of 4 glass segments is 16 cm. But the drawing results in 17 cm of gasses shorter than 16 cm of glasses, which is impossible. That means that the drawing is not to scale, which most likely means that the glasses are not all the same size, which is an implicit assumption in either calculated solution. That really means that the calculated value may not be correct, and the more correct answer to the question is "we can't be sure, but the glass is probably around 13 cm tall."
Glass is 13cm. Easy enough to do in your head. ----- 3 "tops" are 12cm (IE, 29cm-17cm). 1 "top" is thus 4cm. Thus, since the glass + 1 "top" is 17cm, the glass is 17cm minus 4 cm, which is 13cm.
The method would depend on the teacher if in a classroom. One teacher would teach algebra and say show the work. Method one. A another math teacher might say, what's the answer - method 2.
X+y=17; x+4y=29 (assuming they’re all the same dimensions); so subtracting equations we get 3y=12 or y=4 and x or height of each glass is 17-4 or 13.🎉🤡☠️👺👹👻👿👾
I tried doing a solution before watching the video. I guess I just found the height of each "extension' of the cup but didn't apply the next step of finding the individual cup height, eg 17-4 here's my working out, is there a problem with it (i'm a coder so // just means explanation or comment) 2g = 17 // 2 glasses = 17cm 5g = 29 // 5 glasses = 29cm 5g - 2g = 3g // subtract the 5glasses from the 2 glasses 29 - 17 = 12 // which gives us 12 3g = 12 // so 3 glasses is 12cm 1g = 4cm // divided by 3 each side
Hey math friends! If you’re enjoying this video, could you double-check that you’ve liked it and subscribed to the channel? It’s a simple equation: your support + my passion = more great content! Thanks for helping me keep this going - you’re the best!
I'm thinking there is a more direct way. The glasses slide into the one below it somewhat, So each glass can be looked at as the "lower" part of the glass, and the "upper" part of the glass. So the 29cm stack on the left is made up of FIVE glass "uppers" and ONE glass "lowers". Let X = the "lower" part of the glass, which leads to the formula X+5y=29cm. The 17cm right stack is x+2y=17cm. using subtraction, the X's cancel out and you are left with 3y=12. Making y=4. Substituting that into either earlier formula (x+5y=29 or x+2y=17) gives x=9. So "lower" glass 9, plus higher glass 4, =13
A lot of commenters clearly already knew how to solve this problem. The video clearly and concisely explains how to solve it for someone who did not already know.
Both ways are great, and each can be used to cross-check the answer from the other. My own first inclination is the math approach, so it was good to see how to do it graphically, too. I love your videos, Susanne, because you have a talent for simplifying without oversimplifying. Mind Your Decisions!
Great Suzanna. I am 73 and you are bringing back my math skills. Please keep it going - appreciated and you are gorgeous as well. I wish I had during school a maths teacher as you - thanks.
Amazing, I could figure out the answer using method 2 myself. Also, loved how you applied simultaneous equations in method 1.
Thanks for piquing my interest in maths after 2 long decades in school.
I like your puzzles , they take me back 60 years to my maths lessons , which I enjoyed tremendously . I solved this slightly differently ( in my head ) by multiply the short stack by 4 = 68 , subtracting the tall stack ( 4 tops + 1 glass ) = 39 = height of 3 glasses so divide by 3 = 13 .
i remember from my school days that the hardest part of this type of problem for many was describing it as a solvable formula, and where/how to assign the variables and that's where many schoolmates fell down at the first hurdle. If you have a 'math's brain' it's relatively straight forward, and 50+ years later, although i was a grade A maths student then, it takes a little more thinking about now, but still a great process and satisfaction when you solve it. so thanks.
My brain went to Method 1 as soon as I saw the image, because, in math, I'm usually thinking "how can I make an equation out of this?" However, Method 2 makes total sense! Love it!
This was fun, thank you! I used equations to solve it, but I really like your second method.
Nice, that you tried it yourself and that it worked! The beautiful thing about math is, that there are so many ways to solve a problem.
Here's my working it out:
Let a equal the segment of the glass height that doesn't stack. Let b equal the remaining glass height.
29 = 5a + b, 17 = 2a + b
29 - 5a = b = 17 - 2a
12 = 3a, a = 4
b = 17 - 2(4) = 17 - 8 = 9
ans: a + b = 4 + 9 = 13
I used the second method, and came up with 13 cm, just as you did. You can take this problem one step further and determine how much of each of the top four glasses is covered up by the one below it. Namely, if each glass is 13 cm, and 4 cm is exposed, then 9 cm of each glass (13-4) is hidden within the glass below it.
Am binge watching you right now... You are putting me off making my own content - lol :)
I think 13.
Missing value = X
Height of 1 added glass = Y
1. x + y = 17
2. x + 4y = 29
We can subtract "x + y" from "x + 4y" on the left, then 17 from 29 on the right to give us 3y (12) and y (4).
Then we subtract y from "x + y" to get the answer: 17 - 4 = 13.
Simply lovely !!! A beautiful way of solving the Math puzzles !!!
I instinctively used method 2, probably because it has been too long since I had to use ,method 1 in daily life. But it is nice to be reminded of method one, because that is more broadly applicable.
Great, that you could solve it! Yes, equations are usually not a part of our daily lives. 😄
Great video. I prefer the graphical method because that's how I think but I am enjoying reliving algebra again. Your happy greeting is also nice.
x + 4y = 29, x + y = 17. Solving the system of equations gives x = 13 and y = 4. I solved this sitting in my recliner w/o pencil and paper (~30 seconds). Now, I’ll watch your video. Your presentations are usually terrific.
Me too. Nice job
Great video. You remind me of the good teachers I had when I was in school. Very clear, and a good approach to teach. Watching from New Jersey!
Oh wow, thank you so much for your kind feedback and all the best to New Jersey! It’s awesome to reach people from all around the world!
Yay. I got another one right before watching the video.
Thanks for the detailed explanation of the different methods!
I went 29-17=12. 12÷3=4. 17-4=13.
I think my method was kind of a hybrid of the 2.
I did it like you
That's how I did it (in my head). I don't think it's a hydrid of the two , it is the second method.
same
Same here. I didn't even watch the video. So I don't know what are those two methods are and if my method is hybrid or not
Nice. I used the second method to find the answer in under a minute.
They are basically the same method, only the second time it is applied graphically which is very good to explain how the elimination method work when solving a system of equations. In both case we subtract the second equation x+y=17 to the first one x+4y=29 e and we get 3y = 12
I used the graphical method and solved the problem in a few seconds. I simply used 29-17=12. Then I divided 12 by 3 to get 4. Then 17-4=13. It was interesting to see the formulaic approach also, which if I'm honest made this simple problem more complicated. I think this puzzle nicely shows that sometimes diving into maths is not necessary, and other times it is the only way to get an answer.
The two methods are kind of the same. When you subtracted one height from the other, it's the same as subtracting one equation from the other. And when you divided 12 by 3, it's like dividing both sides by three. And then, the final substitution to find the height of the glass.
Yes, the underlying math is the same. However, it is a very different way to approach the problem.
I used the first method to find the results, then confirmed using the second method.
Yes, but it's a different way of thinking about the same thing. That's one of the things I love about maths, that there are so often very different angles to look at fundamentally the same thing
A tip that’s worked well for me teaching math to people who aren’t super comfortable with it. Use different variables, ones that will help them visualize it better. Math people are fine and prefer X and Y, but I’ve found normal people don’t internalize that well. So something like G for the glass, and T for the top. That way they can better think of it in a way that’s simpler to them.
Thank you for this nice idea! I will keep it in mind for my next videos!
I thought G and T was what you put in the glasses..... ;-)
@MathQueenSusanne I remember my calculus teacher, sometimes avoided using letters, used a "blob" instead. Especially with more complicated problems, to represent parts of expressions.
Basically to communicate that the name didn't matter,
Like both ways to get to the Solution! Thanks!
I did it in my head along the lines of the second method: the difference between the two stacks is the taller one has 3 more glasses so I worked out that those 3 glasses added 12 cm to the stack so each glass must add only 4cm to the stack which meant that the height of a glass is 17-4=13. The reason being, the pictures side by side made it very easy to break the stack of 5 glasses into 2 glasses (identical to the nearby stack of 2) and the additional 3.
And I did it a bit differently. I set t=the top of the glasses, and b=the rest of the glass. So I had 5t+b=29, and also 2t+b=17. After solving, the answer will be = t + b.
thanks for the review of solving for two variables.
It has something relaxing to watch you do the math. 😁 I think about the problem for a minute and then I watch your video.
Aaaaw, thank you so much! It’s great, that you enjoy it!
Love these videos! My granddaughter and I like the equation method the best!
These videos are addicting
I used a variation of method 1.
A assumed that the hight of a glass is X and that there is a stacking height that allows 2 glassed to be stacked in 2X -Y cm. Using this for
stack 1: 5X - 4Y = 29
stack 2: 2X - Y = 17
Multiple (2) by 4 and we get: 8X - 4Y = 17 x 4
Subtract stack 1 from this to get: 3X = (17 x 4) -29 = 39
Divide by three to get X = 13cm
Watching from Delaware! You are an excellent teacher! Thank you for keeping my brain cells stimulated!
Awesome, that you watch math videos in your free time!
I used method two to solve it in my head in about 5 seconds. Interestingly, method 2 is basically the same as method 1, just more intuitively and less symbolic.
I agree, but it sometimes helps people to see the other method. The first method is my preference because there is more math! 😉
1) x + 4y = 29 cm
2) x + y = 17 cm => y = 17 cm - x
x + 4(17 cm - x) = 29 cm
3x = 4(17 cm) - 29 cm = 39 cm
x = 13 cm
I did it in my head in less than 10 seconds. How? On the left we have FOUR of the glasses which are protruding outside of another one. On the left hand, we have ONE protruding. The difference is THREE. and 29-17 is 12. 12 is for four minus one protruding glasses so 1 is 4 cm. 17-4 is 13. Thanks.
Exactly how I did it as well
The difference between the stack on the right and the stack in the middle is three glass tops. It's also 12cm taller. So each glass top = 12/3 (ie 4). So if we take that glass top off the centre stack, it will leave us with (17-4) 13cm for an empty glass. And that's our answer.
I used a math approach similar to the author's second method. Substitution: I wrote 17+3y=29 -> 3y =12 -> y=4, therefore x=13. And I checked my work, my brain is almost 70 years old.
I used the second method right off the bat. However, I really like the refresher on finding the height using algebraic expressions.
I used ax+b where x is the number of glasses.
gave a=4 and b=9.
To the optimist, the glass is half full. To the pessimist, it is half empty,. But the realist knows the glass is twice as big as it needs to be...
Been nearly 60 years since I did simultaneous equations, but I still managed to work it out mathematically, using x and y.
I used the equation method - however I subtracted the smaller value from the larger
a+4b=29
a+b=17
subtractubg the two you are left with
3b=12
therefore b = 12/3 = 4
a=17-4 =13
Whilst doing subtracting the larger equation from the smaller still gives the same answer, for me it's not as clean to end up with negative numbers when you don't need to.
29 cm 17 cm 13 cm 17 cm-4 cm=3 cm
Almost correct. The answer is indeed 13 cm (I found that after 1.5 s), but 17 cm - 4 cm = 13 cm
Great example, I totally messed this up but it's easy now. Love both methods.
Are you wearing a 1FCK pullover? I used to live in Kaiserslautern! Small world
X+y = 17. X+4y=29. Y=17-x. X+68-4x =29. -3x=-39. X=13. Y=4.
x + y = 17 (1)
x + 4y = 29 (2)
4 X (1) - (2) = 3x = 4 X 17 - 29 = 68 - 29 = 39
3x = 39
x = 13 cm
Thanks Queen Suzanna
As you said graphical, that triggered graph in my mind. Thus, you have two points (1,17) and (4,29) which generates the equation y = 4x + 13. The y intercept is the height of the glass and the slope the amount sticking out of the stacked glass.
x= height of cup
y= visible amount of cup when stacked
x+4y=29
x+y=17
3y=12
y=4
The cups are 13 cm tall
Danke Susanne, dein wirkliche Stimme! Thank You "Sussy", Your real voice.
I solved this before looking at your solution and I did it graphically. 🙂
Awesome that you successfully tried yourself!
29-17 = 12 and so 3 stacked cups are equal to 12. Divide and each stacked cup is equal to 4. Do 17-4 to get your bottom cup and you have 13.
Which whiteboard are you using ?
Got it right calculated in 10seconds That was way to easy
The difference in height between the two stacks is 12cm. The difference in stack size is 3 cups. Division tells us that each stacked cup adds 4cm of height.
17 - 4 = 13
or
29 - (4*4) = 13
I used the first method. However, I did the subtraction the other way, to avoid negative on both sides.
Thank you, very cool.
Does anyone know the name of the program Susanne is using in these demonstrations? Looks very useful
Well it is 29-17=12 and the 3 portions left over from the left part are all equal so 12/3=4 which means the smaller parts are all 4 so 17-4=13
This can be solved in this way too…29-17 =12
12/3 (three glass are extra from second image) = 4
Than answer is 17-4 =13
Dankeschön ❤❤
I solved the puzzle using the second method, but I prefer your first one
I solved it the equation way, but I like the 2nd one more :-)
I would have used your second example first, but enjoyed all of it
The algebraic solution is much more fun than the visual solution.
Really simple “ 3 segments increase height from 17-29=12. That means each segment is 4cm so the glass is 17-4=13cm.
I always prefer the quick solution without x.
I clicked for the math, stayed for the Queen.
My way of solution ▶
The height of the glasses: x
The height of each glass when placed inside the other: y
⇒
x+4y= 29 cm
x+y= 17 cm
⇒
x+4y= 29
-x-y= -17
⇒
3y= 12
y= 4 cm
x+4y= 29
y= 4
⇒
x= 13 cm ✅
I was really pleased when I had gotten it right
Problem with Poores solved. Just 3 for 4 and 2. Only if you have too stomach.
17-4=13 cm
(29-17)/3 = 4
17-4 =13
The second one seems more straight forward visually. Both are the same in the end though. Cheers 👍💪✌
17-X = 29-4X
17-29 = -4X+X
-12 = -3X
X = 4
17-4=13
29-17=12, 12/3=4, 17-4=13
13 is answer
A+4B = 29
A+B = 17
___________-
3B = 12
B = 4
A=17-4
A=13
Done
x + (4*y) = 29
x + y = 17
I'm an engineer and we often check our answers visually. If you take the 17 cm tall set of 2 glasses and place them on top of the one glass in the 29 cm tall glasses, you'll see that the 17 cm does not quite reach the top of the 29 cm. There are 4 glass segments in that area, and each was calculated as 4 cm, meaning the entire section of 4 glass segments is 16 cm. But the drawing results in 17 cm of gasses shorter than 16 cm of glasses, which is impossible. That means that the drawing is not to scale, which most likely means that the glasses are not all the same size, which is an implicit assumption in either calculated solution. That really means that the calculated value may not be correct, and the more correct answer to the question is "we can't be sure, but the glass is probably around 13 cm tall."
Glass is 13cm.
Easy enough to do in your head.
-----
3 "tops" are 12cm (IE, 29cm-17cm).
1 "top" is thus 4cm.
Thus, since the glass + 1 "top" is 17cm, the glass is 17cm minus 4 cm, which is 13cm.
Ain't no thang...
@3:14 she says forex?
I prefer the classical solution with a system of equations. It's more immediate for me.
29-17=12
12/3=4
17-4=13
My glasses were full of red wine, so I started by emptying them.
When I finished to drink all of them, I was so drunk, I can't do the math...
i prefer both method and your funny explanation
except you cant prefer both methods :3
am i dumb or do you also had a german yt channel?
You’re right, I also have the German channel @MathemaTrick 😊
The method would depend on the teacher if in a classroom. One teacher would teach algebra and say show the work. Method one. A another math teacher might say, what's the answer - method 2.
X=17-((29-17)/3)
X= 13
+3 glasses = +12 cm, so each + = 4cm
29 -12 =13cm
5 seconds in my head
The answer is 13 cm
X+y=17; x+4y=29 (assuming they’re all the same dimensions); so subtracting equations we get 3y=12 or y=4 and x or height of each glass is 17-4 or 13.🎉🤡☠️👺👹👻👿👾
I tried doing a solution before watching the video. I guess I just found the height of each "extension' of the cup but didn't apply the next step of finding the individual cup height, eg 17-4
here's my working out, is there a problem with it (i'm a coder so // just means explanation or comment)
2g = 17 // 2 glasses = 17cm
5g = 29 // 5 glasses = 29cm
5g - 2g = 3g // subtract the 5glasses from the 2 glasses
29 - 17 = 12 // which gives us 12
3g = 12 // so 3 glasses is 12cm
1g = 4cm // divided by 3 each side
Genuine question: Why subtract 4 from both sides instead of doing x + 4 = 17 = x = 17 - 4 = 13
Hottest math pro ever!
Make your life easuer by subtracting in the reverse order thus eliminating the negative signs.
And 30 it only take 30 second
Solved using first method
29-17=13 17-13=4 13+4+4+4+4=29 13+4=17
quand on te fait passer un test d'embauche pour un poste de design engineer, il faut mieux répondre en moins de 5mn