By taking 3' off it
Add alot of iodine
One possibility is (21 - 21) * 13 + 24 = 24
Drain it.
24 foot round pool would be 24 feet across from the middle of the pool basically measure the diameter of the pool.
Add salt
Simply put any pool can be a salt water pool, even an above ground pool.
21/24 and 20/24
Average of 21, 24, 21 and 23 = (21+24+21+23)/4 = 22.25
21 24 means : The time is 21 ( p.m ) and 24 minutes .
yes, you can turn a pool into a giant hot tub.
24 what?
24