Question

If y varies directly as x, and y = 5 when x = 6 what is the value of y when x = 18

Answer 1

y = 15

Explanation:

given y varies directly as x , then the equation relating them is

y = kx ← k is the constant of variation

to find k, substitute y = 5 when x = 6 into the equation

5 = 6k ( divide both sides by 6 )

`(5)/(6)` = k

y =
`(5)/(6)` x ← equation of variation

when x = 18 , then

y =
`(5)/(6)` × 18 = 5 × 3 = 15