Question

Given that V= πr^2h. Make r the subject of the formula.

Using the result from the above,find r when V = 81 cm3, π = 4 and h = 9cm​

Answer 1

The answer is
`r=(3)/(2)\ cm.`

Explanation:

Given:

V= πr²h.

V = 81 cm3,

π = 4 and

h = 9cm​.

Now, making r the subject of the formula using the result from the above, find r.

So, to get the value of r:

`V=\pi r^2h`

`81=4* r^2* 9`

`81=36r^2`

Dividing both sides by 36 we get:

`(81)/(36) =r^2`

Using square root on both sides we get:

`(9)/(6) =r`

`(3)/(2) =r`

`r=(3)/(2).`

Therefore, the answer is
`r=(3)/(2)\ cm.`