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

Answer:

The answer is $r=\frac{3}{2}\ cm.$

Step-by-step 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:

$V=\pi r^2h$

$81=4\times r^2\times 9$

$81=36r^2$

Dividing both sides by 36 we get:

$\frac{81}{36} =r^2$

Using square root on both sides we get:

$\frac{9}{6} =r$

$\frac{3}{2} =r$

$r=\frac{3}{2}.$

Therefore, the answer is $r=\frac{3}{2}\ cm.$