Question

Assume that y varies directly with x. If y = -5 when

X = 12.5, find x when y=15. Enter in any fractions
using a / (e.g. "1/2" is the same as 1/2

Answer 1

Thus, the value of x = -36 when y = 15

Explanation:

We know that if y varies directly with x, we can express the relationship such as

y ∝ x

y = kx

k = y/x

where 'k' is called constant of variation.

Given

y = -5

x = 12

Using the equation

k = y/x = -5/12

Thus, the value of k = -5/12

Finding x when y = 15

y = 15

k = -5/12

substituting y = 15 and k = -5/12 in the equation

y = kx

15 = -5/12 (x)

15×12 = -5x

180 = -5x

divding both sides by -5

-5x/-5 = 180/-5

x = -36

Thus, the value of x = -36 when y = 15