Hi there, thanks for sharing the video. I currently work as a tutor in Singapore, and one of the subjects I teach is Primary School Math. I noticed you were having a bit of trouble drawing the models to solve the question at 16:28. Actually, it's quite common and natural for most people who've just started dealing with models to make the mistake you did. Haha. So, I've decided to explain how it should be done. I've set the explanation out in a step-by-step way, exactly the way you would do it when explaining to a student. The question was: The ratio of Sue's age to Bob's age is 3 to 7. The ratio of Sue's age to Joe's is 4 to 9. The ratio of Bob's age to Joe's is ______. To solve the problem, you need to draw 2 separate models. How To Draw Model 1: Step 1: Draw the figure to represent Sue's age relative to Bob's, i.e., 3 units. Label it "S". Step 2: Directly below that, draw the figure to represent Bob's age relative to Sue's, i.e. 7 units. Label it "B". These 2 figures are paired together and form the 1st model /diagram. How To Draw Model 2: Step 3: Draw the figure to represent Sue's age relative to Joe's, i.e., 4 units. However, take note that the length of the figure must be the same as that in Step 1. This is based on the reasoning that when using models, figures of the same length represent identical value. Label it "S". Step 4: Directly below that, draw the figure to represent Joe's age relative to Sue's, i.e., 9 units. Label it "J". These 2 figures are paired together and form the 2nd model /diagram. The next part is critical. As you noticed while doing it your way, you had trouble comparing Bob's age to Joe's diagramatically because the figures were not drawn to scale. In other words, for it to work visually, one needs to ensure that Sue's model (which functions as the basis of comparison between Bob and Joe), is identical. In order to do this, one simply needs to find the lowest common multiple of 3 and 4, which is 12. Now, all you need to do is go back to the models and reflect this information. Go back to Model 1 and do the following: Step 5: On the figure that you drew to represent Sue's age in Step 1, divide each of the 3 units into 4. This will give a total of 12 units. Step 6: On the figure that you drew to represent Bob's age (relative to Sue's age in Step 2), also divide each of the 7 units into 4. This gives a total of 28 units. Go back to Model 2 and do the following: Step 7: On the figure that you drew to represent Sue's age in Step 3, divide each of the 4 units into 3. This will give a total of 12 units. Step 8: On the figure that you drew to represent Joe's age (relative to Sue's age in Step 4), also divide each of the 9 units into 3. This will give a total of 27 units. Now, you can easily look at the figures drawn in Step 6 and 8 and compare them. The ratio of Bob's age to Joe's would therefore be 28:27. Actually, for this type of questions, students only draw the models in the beginning when there are trying to get used to the question. Most (good) students just don't bother drawing the models at all because it is too time-consuming and unnecessary once you get the logic of it. So, they simply start by finding the lowest common multiple of 3 and 4. From there, they know to do 7x4 and 9x3. So, if you do it like that, it'll only take you a few seconds to solve this SAT question. I hope that helps.
Hi there, just to share a few of my thoughts on the SAT problem : "Joe can mow a lawn in 3hrs. Moe can mow a lawn in 5hrs. How long will it take if they do it together?" (30:30) Actually, I don't think you can solve it by doing models, but if I had to do it in a way that is as close to the Singaporean way as possible, I would do the following: The ratio of Moe's speed to Joe's speed is 3 to 5, or 1 to 1 and 2/3. Logically speaking, if we change the question a bit and say they were working at the same speed (i.e., Joe also takes 5h), then the ratio would be 1:1, and the way to solve it would simply be 5 divided by (1 plus 1)= 2.5hrs. Using that same way of thinking, all we have to do is take 5 divided by (1 plus 1 and 2/3)=15/8hrs. Again, if you were doing it during the SAT, it would only take a few seconds. I hope that helps!
Box of chalk and stapler problem starts at 21:00 or 21:37.
Hi there, thanks for sharing the video. I currently work as a tutor in Singapore, and one of the subjects I teach is Primary School Math. I noticed you were having a bit of trouble drawing the models to solve the question at 16:28. Actually, it's quite common and natural for most people who've just started dealing with models to make the mistake you did. Haha. So, I've decided to explain how it should be done. I've set the explanation out in a step-by-step way, exactly the way you would do it when explaining to a student.
The question was: The ratio of Sue's age to Bob's age is 3 to 7. The ratio of Sue's age to Joe's is 4 to 9. The ratio of Bob's age to Joe's is ______.
To solve the problem, you need to draw 2 separate models.
How To Draw Model 1:
Step 1: Draw the figure to represent Sue's age relative to Bob's, i.e., 3 units. Label it "S".
Step 2: Directly below that, draw the figure to represent Bob's age relative to Sue's, i.e. 7 units. Label it "B".
These 2 figures are paired together and form the 1st model /diagram.
How To Draw Model 2:
Step 3: Draw the figure to represent Sue's age relative to Joe's, i.e., 4 units. However, take note that the length of the figure must be the same as that in Step 1. This is based on the reasoning that when using models, figures of the same length represent identical value. Label it "S".
Step 4: Directly below that, draw the figure to represent Joe's age relative to Sue's, i.e., 9 units. Label it "J".
These 2 figures are paired together and form the 2nd model /diagram.
The next part is critical. As you noticed while doing it your way, you had trouble comparing Bob's age to Joe's diagramatically because the figures were not drawn to scale. In other words, for it to work visually, one needs to ensure that Sue's model (which functions as the basis of comparison between Bob and Joe), is identical. In order to do this, one simply needs to find the lowest common multiple of 3 and 4, which is 12. Now, all you need to do is go back to the models and reflect this information.
Go back to Model 1 and do the following:
Step 5: On the figure that you drew to represent Sue's age in Step 1, divide each of the 3 units into 4. This will give a total of 12 units.
Step 6: On the figure that you drew to represent Bob's age (relative to Sue's age in Step 2), also divide each of the 7 units into 4. This gives a total of 28 units.
Go back to Model 2 and do the following:
Step 7: On the figure that you drew to represent Sue's age in Step 3, divide each of the 4 units into 3. This will give a total of 12 units.
Step 8: On the figure that you drew to represent Joe's age (relative to Sue's age in Step 4), also divide each of the 9 units into 3. This will give a total of 27 units.
Now, you can easily look at the figures drawn in Step 6 and 8 and compare them. The ratio of Bob's age to Joe's would therefore be 28:27.
Actually, for this type of questions, students only draw the models in the beginning when there are trying to get used to the question. Most (good) students just don't bother drawing the models at all because it is too time-consuming and unnecessary once you get the logic of it. So, they simply start by finding the lowest common multiple of 3 and 4. From there, they know to do 7x4 and 9x3. So, if you do it like that, it'll only take you a few seconds to solve this SAT question.
I hope that helps.
Don't be a smartass. You're a just tutor, not a fucking professor. Chillax dickhead!
@@opendebate wat
How, or where, can I get more information about the SM? I mean, I need someone that can provide me a training.
thank you very much for sharing the video!
Hi there, just to share a few of my thoughts on the SAT problem : "Joe can mow a lawn in 3hrs. Moe can mow a lawn in 5hrs. How long will it take if they do it together?" (30:30)
Actually, I don't think you can solve it by doing models, but if I had to do it in a way that is as close to the Singaporean way as possible, I would do the following:
The ratio of Moe's speed to Joe's speed is 3 to 5, or 1 to 1 and 2/3.
Logically speaking, if we change the question a bit and say they were working at the same speed (i.e., Joe also takes 5h), then the ratio would be 1:1, and the way to solve it would simply be 5 divided by (1 plus 1)= 2.5hrs.
Using that same way of thinking, all we have to do is take 5 divided by (1 plus 1 and 2/3)=15/8hrs.
Again, if you were doing it during the SAT, it would only take a few seconds. I hope that helps!
Hi
Stop saying foolish things