Question

The variable is directly proportional to the variable . If y = 10 when x = 6, what is the value of y when x = 15?

Answer 1

y = 25

Explanation:

Given that the quantities are proportional then the equation relating them is

y = kx ← k is the constant of proportion

To find k use the condition y = 10 when x = 6

k =
`(y)/(x)` =
`(10)/(6)` =
`(5)/(3)`

y =
`(5)/(3)` x ← equation of proportion

When x = 15, then

y =
`(5)/(3)` × 15 = 5 × 5 = 25