Ratios and Proportions

Question 1

When setting up proportion questions, what is the easiest way to set up the problem?

Answer 1

Weight_A/cost_A = Weight_B/Cost_B

Question 2

What should you do when dealing with proportion questions that contain decimals?

Answer 2

Round up/down and estimate the answer

Question 3

What should you do if you get a ratio problem set up like 5 : 7 : 8?

Answer 3

Set up the equation to find the unit value of the ratio 5x : 7x: 8x

When given a ratio, put in “x”s into each element of the ratio, and set the actual quantity you’re given equal to its counterpart that is in terms of “x”. Then once you find “x”, you can solve for any element of the ratio.

Total = 20x

Question 4

How to you turn a fraction into a percent?

Answer 4

Example

3/20 x 100/1 = 15%

Question 5

What’s the best way to find 20% of 60 on the GMAT?

Answer 5

Find what 10% of 60 is (6) and then multiply by 2 = 12

Question 6

Make sure you use benchmarks to estimate answer choices… What are the benchmarks for 1/5, 1/6, 1/7, 1/8, 1/9.

Answer 6

1/5 = 0.2

1/6 = 0.167 = 16-2/3 %

1/8 = 0.125

1/9 = 0.11

Question 7

If there is only one decimal answer out of all the other options, what does that tell you?

Answer 7

That answer is probably wrong.

Question 8

If you see one of the answers in the question, what does that tell you?

Answer 8

It is probably not the right answer.

Question 9

If your strategy of the 10% of a certain number doesn’t work, what is the next strategy?

Answer 9

X% of y = y% of x

28 x 25% = 25% x 28

= 7

Question 10

What should you focus on in mixture questions?

Answer 10

What quantity DOES NOT change.

Question 11

What is the balancing method when doing averages?

Answer 11