Question

Suppose that y varies directly as x and y=10 when x=8. Find the value of x when y=30

Answer 1

x = 24

30/10 = 3

So, 3x = 24

Answer 2

Varies directly:
`(y)/(x) = k`

First, solve for k. Then replace the k-value into the equation and cross multiply to solve for the missing variable.

`(10)/(8) = k` ⇒
`(5)/(4) = k`

`(30)/(x) = (5)/(4)`

30(4) = 5(x)

6(4) = x divided both sides by 5

24 = x

Answer: 24