Question

The value of y varies directly with x. if y = 20 and x = 30, what is the value of y if x = 1?

A. 200
B. 2/3
C. 110/3
D. 9/2

Answer 1

B. 2/3

Explanation:

If y directly varies with x, then y = kx where k is a constant

Given that when y = 20 when x = 30 we get the equation: 20 = k x 30

or

20 = 30k

Dividing by 30 both sides and switching sides gives

k = 20/30 = 2/3

The equation becomes
y = 2/3 x

Therefore if x = 1 we get

y = 2/3 x 1 = 2/3

Choice B