Question

The function f(x) varies directly with x and f(x)=90 when x = 30. What is f(x) when x = 6?

Answer 1

Answer: just took the test f(x) = 18

Explanation:

Answer 2

f(x)=18

Explanation:

We are given that
`f(x) \propto x`

So,
`f(x) = kx` ---1

Where k is the constant of proportionality

f(x)=90 when x = 30

Substitute the values in Equation 1

`90 = k(30)`

`3 = k`

So, equation becomes :
`f(x) = 3x`

Now find f(x) when x = 6

Substitute x = 6 in equation 2

`f(x) = 3(6)`

`f(x) = 18`

Hence f(x)=18 when x = 6