Please explain how to solve...?

Question

Joe can fill a pool using buckets in 30 minutes. Bill can fill it in 45 minutes and Stan can fill it in 90 minutes. If they work together, how long will it take them to fill the pool?

Answer is 15 minutes. Please explain!

Answer 1

take the greatest common factor of the three numbers.
(30/1) + (45/1) + (90/1) = (90/3) + (90/2) + (90/1) = 15 min

Answer 2

Logically, if you take 15 minutes, Joe can fill half the pool, bill can fill 1/3 the pool and Stan can fill 1/6th the pool. Now, how do you put your problem together to solve this.

The answer is to consider the equation
volume = volume/time x time, which is analogous to distance = speed x time.
If the volume is one pool, Joes volume/time is 1 pool/30 minutes, and so on. Then you have
1 pool = [1/30 + 1/45 + 1/90] (time) or
1 pool= 6/90 x time . As wanted, time = 15 minutes.

Answer 3

In a minute, Joe can fill 1/30 of the pool. Bill can fill 1/45 of the pool. Stan can fill 1/90 of the pool. Working together they fill:

1/30 + 1/45 + 1/90 of the pool.

3/90 + 2/90 + 1/90 = 6/90 = 1/15

Each minute, all three fill 1/15 of the pool. The pool will be filled in 15 minutes.

Answer 4

In 1 minute Joe can fill 1/30 part of it,Bill can fill 1/45 part of it and Stan can fill 1/90 part of it,if each of them work individually.
If they work together,in 1 minute they can fill
1/30+1/45+1/90 part of the pool
=3/90+2/90+1/90
=6/90
=1/15 part of the pool
Therefore,working together they can fill the pol in 1divided by 1/15 or 15 minutes.

Answer 5

there is a formula to solve questions like this

1/t=1/30+1/45+1/90
t=15 minutes
hope that helps