Question

If y varies directly as x and y is 18 when x is 5 which expression can be used to find the value of y when x is 11?

Answer 1

y = kx where k is a constant Thats direct variation.

plug in given values:-

18 = k * 5

k = 18/5 = 3.6

so the equation of variation is y = 3.6x

when x = 11, y = 3.6 * 11 = 39.6 Answer

Answer 2

The value of y is
`(198)/(5)` or 39.6.

Explanation:

It is given that y varies directly as x and y. It means y is directly proportional to x.

`y\propto x`

`y=kx` .... (1)

where, k is constant of proportionality.

It is given that y is 18 when x is 5.

Substitute y=18 and x=5 in equation (1).

`18=k(5)`

Divide both sides by 5.

`(18)/(5)=k`

The value of k is
`(18)/(5)`. So, the relation between x and y is

`y=(18)/(5)x` .... (2)

We need to find the value of y when x=11.

`y=(18)/(5)(11)`

`y=(198)/(5)`

`y=39.6`

Therefore the value of y is
`(198)/(5)` or 39.6.