Question

If f(x) varies directly with x and f(x) = 4 when x = 12, then what is the value of f(x) when x = 60?

20

180


5

300

Answer 1

ANSWER


`f(60)=3*60=180`

Step-by-step explanation
We were given that

`f(x)`
varies directly as

`x.`

We can write this mathematically as,


`f(x) \propto \: x.`

This implies that,


`f(x) = kx`
where k is the constant of variation.


`f(4)=4k`

This implies that,


`4k=12`


`k = 3`

The equation becomes


`f(x)=3x`

When
`x=60`


`f(60)=3*60=180`