Question

The value of y varies directly as x and y is 15 when x is 5 what is the value of y when x is 19

Answer 1

y = 57

Explanation:

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

y = kx ← k is the constant of variation

To find k use the condition y = 15 when x = 5

k =
`(y)/(x)` =
`(15)/(5)` = 3, hence

y = 3x ← equation of variation

When x = 19 then

y = 3 × 19 = 57

Answer 2

Divide the known y and x:

15/5 = 3

Y is 3 times as much as x.

Now multiply X by 3 to find y:

Y = 19 * 3 = 57