Question

Suppose y varies directly with x and y=20 when x = 10. What is the value of y
when x = 30?

Answer 1

y = 60

Explanation:

Given that y varies directly with x then the equation relating them is

y = kx ← k is the constant of variation

To find k use the condition y = 20 when x = 10, then

20 = 10k ( divide both sides by 10 )

2 = k

y = 2x ← equation of variation

When x = 30, then

y = 2 × 30 = 60