# Thread: Pls solve this Aptitude Question????

1. YahooHoo
Join Date
Aug 2007
Posts
2

## Pls solve this Aptitude Question????

Pipe A can fill in 20 minutes and Pipe B in 30 mins and Pipe C can empty the same in 40 mins.If all of them work together, find the time taken to fill the tank???
1)17 1/7 MINS
2)20 MINS
3)8 MINS

pls explain in detail

2. YahooHoo
Join Date
Aug 2007
Posts
1
Let x = no. of minutes to fill the tank.

Equation:
x/20 + x/30 - x/40 = 1
6x/120 + 4x/120 - 3x/120 = 1
7x/120 = 1
7x = 1 * 120
x = 120/7
x = 17 1/7

The answer is 1) 17 1/7 MINS

3. YahooHoo
Join Date
Aug 2007
Posts
1
Let the volume of tank be V
A can fill tank in 20 min => In 1 min A can fill up v/20 of the tank

lly

B can fill tank in 30 min => In 1 min B can fill up v/30 of the tank

lly

C can empty tank in 40 min =>In 1 min C can empty v/40 of the tank

Let t be the time taken for the tank to be completly filled i,e Volume V

=> volume filled by A in t min + volume filled by B in t min +
volume emptied by c in t min = V
=> t(V/20)+t(V/30)+t(-V/40) = V
=> tV(1/20+1/30-1/40)= V
=> t= 120 / 7
= 17 1/7

4. YahooHoo
Join Date
Aug 2007
Posts
1
its 1 - 17 +(1/7)

5. Entry Level Fresher
Join Date
Jun 2009
Posts
1

## explanation

Originally Posted by rakesh
Pipe A can fill in 20 minutes and Pipe B in 30 mins and Pipe C can empty the same in 40 mins.If all of them work together, find the time taken to fill the tank???
1)17 1/7 MINS
2)20 MINS
3)8 MINS

pls explain in detail
1/20+1/30-1/40=7/120.... inverse of it is 120/7 that is 17 1/7 mins..