Question

X varies directly as y. If x is 9 when y is 4, find x when y is 8.

a) Write the variation.
b) Find x when y is 8.

Answer 1

Explanation:

X ∝ y

introducing proportionality constant , we have

x = ky

given : x = 9 when y = 4 , substitute the given values into the equation in order to get the constant

i.e 9 = k x 4

k = 9/4

substitute k = 9/4 into the equation in order to get the formula connecting x and y

⇒ x = 9/4 y

(b) To find x when y = 8, substitute the value of y into the formula

i.i x = 9/4 x 8

x = 9 x 2

x = 18