Question

If y varies directly with x, find the value of y when x = 27 for the direct variation with the given information. y = 7 when x = -9 y =​

Answer 1

Given:

y varies directly with x,

It is given that y = 7 when x = -9.

To find:

The value of y when x = 27 for the direct variation.

Solution:

It is given that y varies directly with x, so

`y\propto x`

`y=kx` ...(i)

Where, k is the constant of proportionality.

It is given that y = 7 when x = -9. Putting these values in (i), we get

`7=k(-9)`

`-(7)/(9)=k`

Putting
`k=-(7)/(9)` in (i), we get

`y=-(7)/(9)x`

Putting
`x=27`, we get

`y=-(7)/(9)(27)`

`y=-21`

Therefore, the required value is
`y=-21`.