If y varies directly with x and y = 1 when x = 15, how do you find x when y = 8?

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Answer 1 · 2015-10-19T19:54:34

# **x = 120** #

The equation for direct variation is y =kx where k represents the constant of variation.

When y = 1 and x = 15 the equation would translate to

1 = k(15)

To solve for k algebraically, divide by 15 on both sides of the equation.

#1/15 = k(15)/15#

This solves to

#k = 1/15#

To determine x when y = 8
The equation becomes

#8 = 1/15(x)#

Multiply by 15 on both sides of the equation in order to isolate x

#(15)8 = (15)1/15(x)#

#x = 120#