Question

Select the correct answer. the variable y varies directly as x. when x = 20, y = 12. what is the value of y when x = 15? a. 7 b. 9 c. 18 d. 25

Answer 1

b. 9

Explanation:

"y varies directly as x" or "y is directly dependent on x" means that the 2 variables have the following relationship :

y = kx

we have to find the factor "k". and we do this by using the first given pair of x and y values.

x = 20, y = 12

12 = k×20

k = 12/20 = 3/5

when x = 15, we have then

y = (3/5)×15 = 3× 15/5 = 3×3 = 9