Question

Suppose that y varies inversely with x. Given x=-3 when y=-105. Find y when x=15

Answer 1

21

Explanation:

It is given that y varies inversely with x.

`y\propto (1)/(x)`

`y=(k)/(x)` ...(i)

where, k is constant of proportionality.

It is given that x=-3 when y=-105. Substitute these values in equation (i), to find the value of k.

`-105=(k)/(-3)`

`-105* (-3)=k`

`315=k`

Now,

`y=(315)/(x)`

Substitute x=15 in the above equation.

`y=(315)/(15)`

`y=21`

Therefore, the value of y is 21 when x=15.