Question

The variables x and y vary directly, and y=10y=10 when x=2x=2. Write an equation that relates x and y. What is the result when x=9?

Answer 1

y = 5x and y = 45

Explanation:

since x and y vary directly, then

y = kx ← k is the constant of variation

to find k use the given condition y = 10 when x = 2

k =
`(y)/(x)` =
`(10)/(2)` = 5

⇒ y = 5x ← is the equation that relates x and y

when x = 9 then y = 5 × 9 = 45