Question x-y-1-
| x | y |
| 1 | 4 |
| 3 | 12 |
| 5 | 20 |
| 40 | k |
In the table above, the ratio of y to x for each ordered pair is constant. What is the value of k ?
28
36
80
160
x y 1 4 3 12 5 20 40 k In the table above, the ratio
Medium-difficulty · SAT Math · Ratios, Rates, and Proportional Relationships — Direct/inverse proportionality. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.
Answer explanation
Choice D is correct. Since the ratio of y to x is constant for each ordered pair in the table, the first row can be used to determine that the ratio of y to x is 4 to 1. The proportion 
can be used to solve for k. Multiplying each side of the equation by 40 yields 
.
Choice A is incorrect. This is the value of y when the value of x is 7, not 40. Choice B is incorrect and may result from subtracting 4 from 40 instead of multiplying 40 by 4. Choice C is incorrect and may result from incorrectly setting up the proportion.
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