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 By: shirley wee (offline)  Wednesday, April 11 2012 @ 09:31 AM CDT (Read 1213 times)
shirley wee

Tap A can fill an empty tank in 5 mins. When tap A and B are turned on at the same time, they can fill the empty tank in 3 mins. How long does it take for Tap B to fill the empty tank?

Chatty

Registered: 02/28/12
Posts: 68

 By: sugengz (offline)  Wednesday, April 11 2012 @ 11:14 AM CDT
sugengz

Tap A
5 min ----> 1 tank
1 min ----> 1/5 tank

Tap A + Tap B
3 min ----> 1 tank
1 min ----> 1/3 tank

In 1 min Tap B fill....
1/3 - 1/5 = 2/15
1 min ----> 2/15 tank
15/2 min ----> 1 tank

Therefore Tap B will fill the tank in 7.5 min

Newbie

Registered: 03/16/10
Posts: 4

 By: MathIzzzFun (offline)  Wednesday, April 11 2012 @ 05:18 PM CDT
MathIzzzFun

Quote by: shirley wee

Tap A can fill an empty tank in 5 mins. When tap A and B are turned on at the same time, they can fill the empty tank in 3 mins. How long does it take for Tap B to fill the empty tank?

Hi

In 5 mins, Tap A fills 1 tank
In 15 mins, Tap A fills 3 tanks

In 3 mins, Tap A + Tap B fills 1 tank
In 15 mins, Tap A + Tap B fills 5 tanks

In 15 mins, Tap B fills 2 tanks
So, Tap B fill 1 tank in 15/2 = 7.5 min

cheers.

Chatty

Registered: 04/02/10
Posts: 36

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