What is the LCD? 1/9 + 7/30
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- Опубліковано 12 гру 2022
- How to find the LCD (lowest common denominator).
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I have made it past Dif EQ before I discovered this channel. I am absolutely shock at how bad some of my basic skills are. I never grasped these early skills that would have made my life so much easier. I spent way too much time making sometimes a long list of multiples and then matching them up for a LCD. Sometimes I would just resort to multiplying the denominators and then reducing the fraction. I don't recall ever being taught this tree method in my youth and I started math again at aged 42 in trigonometry. I must say this method is intuitive for me and can just do in my head. I watch this channel all the time just to challenge my brain and pick up some basic skills you wouldn't want to ask your college instructor about in the middle of calc 2.
Very nice and clear. Even though I often have to do supposedly advanced maths, I'd forgotten how to do this! Thank you
90. Did it by inspection, but could've used the GCF of 3. Took about 45 seconds. Good problem!
Seems very complicated to me whereas if you understand your times tables 9 * 10 is 90 and three times 30 is 90 and you have arrived at the LCD since both 9 and 30 are multiples of 90.
That’s the way I taught it. Thanks for sharing. I like the way you explained taking the biggest power of 3, take the highest power of 3. Awesome
Thank you so much!
How I worked this out was 9x30 = 270 now 1/9 + 7/30 I made it 1x30 = 30 and 9x7 = 63 = 93 over 270 Now to make it to the lowest number 93 and 270 I can divide by 3 = 31 /90
The way I did it, I get 30 no, 60 ,no 90 ,yes. Both 9 and 30 can divide into 90.
That is the way I used to do it but if you ever get into higher math that method will cause you a headache. Trust me as that was the only way I knew to do it.
Good videos...thanks
The first question was easy. The second question freaked me out for a second...and then I realized 1408 is just 4*176... Actually figured that out by reducing/simplifying 2/176...it's 1/88...just to get a smaller fraction to work with and then, just for kicks, tried dividing 1408 by 88... Surprise, surprise, surprise... so 1408 IS your LCD.
I figured out already that the LCM between 9 and 30 is 90. The GCF is 3, and you divide one of the denominators by 3, then multiply by the other denominator, and you get 90. Either 9 times 10 equals 90, or 3 times 30 equals 90. The new equivalent fractions are: for 1/9 plus 7/30, the equivalent fractions are 10/90 plus 21/90, for a sum of 31/90.
Also, just for the record, the answer to the other problem you wrote down is 19/1408. With 3/1408 plus 2/176, the LCD between 1408 and 176 is 176 itself. Just take 176 and multiply by 8 and you get 1408. The equivalent fractions are 3/1408 plus 16/1408, and your final answer is 19/1408.
OK!
This way seems far to easy for the experts of today. :D
I got 90 by prime factoring thanks to tc math
That one was easy for me even though I didn't do it the best way. I could easily spot that 30 could be multiplied by 3 to come up with 90 which was easy. I then did the rest of the math which gave me 31/90 which I could quickly see as not being able to be simplified which affirmed 90 as being the LCD. Of course I can't do this with larger more complicated denominators within a few seconds as I did with the example problem.
Correct, but He's trying to demonstrate the toolbox at hand for more complicated situations. Foundations are good, I suppose
@@robertakerman3570 Yes, I know that. I did mention I didn't do it the best way. His way is the best way and covers all scenarios. The example program was easy and I did it all in my head in less than 10 seconds. That won't always be the case.
@@fredflintstone8048 The best part is that U must have had great Instructors. May We count Our blessings.
@@robertakerman3570 My instructors were fantastic and well beyond me. I should have paid far better attention and studied harder at the time. I've had to go back later in life and relearn many things due to a need I had for using those things in my field of work.
I agree, lets count our blessings.
@@fredflintstone8048 Fortunately, when I was in that position; We had calculators(Praise Be).
The final answer is 31/90
Without working anything out I'm tempted to say 90
1/9 + 7/30 = 10/90 + 21/90 = 31/90 which cannot be simplified
but let's just multiply 9 by 30 to get 'a common denominator'' (but not the lowest)
1/9 + 7/30 = 30/270 + 63/470 = 93/270 which can be simplified to 31/90
Greetings from the BIG SKY. A new puzzle.
31/90
3
31 over 90
30
31/90 is the answer... The LCD is 90, not 270 (which is 9 * 30).
90 ... 31/90
How does 3 x 3 end up as 3 squared? Why is there a little '2'? Since it is times 3 why isn't it a little '3'? Why isn't 10 prime?
Oh dear. You need to go way more basic.
10 is not prime because it can be broken down into smaller factors (2x5).
Powers do not mean that the base number is multiplied by the power. They mean that the base number is multiplied by itself the number of times indicated by the power.
So, if the base is 3, then 3 squared = 3 multiplied by itself (3x3)
And 3 cubed (base 3 with a little 3) = 3x3x3
Find the LCD; exactly the same way that I was taught in school back in 1960.
9 = 3 x 3
30 = 3 x 10
LCD = 3 x 3 x 10 = 90
I get 90, 6×5×3.
I got the answer by increasing 30 until I got the right answer: 30,60, 90. Ninety!! That's it!!! However, I don't understand what you did with the first term. Using your method, it seems to me that the LCD should be calculated as follows: 3x3x. 2x3x5=270. That's the wrong answer, but isn't that the answer you get by using your method?
Yes, that’s what I thought. I would simply look at the largest denominator (in this case 30), then keep adding 30 until I came to a number that the smaller denominator (in this case 9) goes into without a remainder.
But that method would be hard work with bigger and more difficult numbers, or if several fractions with different denominators were being added together.
I also agree with what you said about the prime factors. He did, however, say that, if the denominators had the same prime factor, only one should be used, and that one should be the one with the highest power. He didn’t explain why though. I guess it would make the video too long. But I would like to see another video explaining why.
LCD is 90 (31/90)
90
How about 90!
Yes 90 LCD
270 ?
Nope , 90
LCD=90
انا من جيل جبر السبعينات وحلي لها ابسط من اطالتك ومباشرة فإن العامل المشترك الأصغر هو 90 والجواب 31/90 وانت لم تذكر الجواب النهائي رغم الإطالة
Who cares about the LCD just find the fastest common denominator, 270, and then reduce if needed. 31/90
Number 2 final answers is 19/1408 it’s not easy to get it 😂
12 minutes to do a 5 second in the head equation...
I agree. Well, maybe ten seconds.
Too much beating around the bush during the introduction. 0/100
This guy spends 66 percent of the time talking about NOTHING. 8 minutes of NOTHING. Lesson starts at 06:50 ish
Blah, blah, blah...3:32.
90k you just wasting your breath. Find a permanent job
31/90
3
90
19
3
3
31/90
31/90