Question

Can u show me how u get the answer​

Answer 1

Explanation:

$p1 \times v1 = p2 \times v2$

$p1 = initial \: pressure \\ v1 = initial \: volume \\ p2 = final \: pressure \\ v2 = final \: volume$

You're looking for p2. So, divide both sides by v2...

$\frac{p1 \times v1}{v2} = p2$

volume of a cylinder is

$h \times \pi \: \times {r}^{2}$

let's assume r = 1

$\frac{p1 \times (20cm \times \pi)}{(60cm \times \pi)} = p2$

the Pi's cancel out, the 20/60 can be reduced to 1/3.

So you end up with

$p1 \times \frac{1}{3} = p2$

or as the book shows....

$\frac{1}{3} p$