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A water tank has three taps A, B, and C. A fills four buckets in 24 mm, B fills 8 buckets in 1 hour and C fills 2 buckets in 20 minutes. If all the taps are opened together a full tank is emptied in 2 hours. If a bucket can hold 5 litres of water, what is the capacity of the tank?

1. 120 litres
2. 240 litres
3. 180 litres
4. 60 litres

Emptying the tank is nothing but filling some number of buckets as determined the rate of filling of the pipes A,B and C..So this is a reverse  question basically , reverse in the sense that time taken to empty the tank is given so we are given the time interval for which the pipes operate which is 2 hours = 120 minutes as mentioned in the question

Given filling rate of pipe A  =  4 buckets in 24 minutes

Hence number of buckets A will fill in 120 minutes = 4 * 5  =  20 buckets = 100 litres  [ As 1 bucket = 5 litres given ]

Similarly

Filling rate of pipe B  =  8 buckets in 60 minutes

Hence number of buckets B will fill in 120 minutes = 8 * 2  =  16 buckets = 80 litres

Filling rate of pipe C  =  2 buckets in 20 minutes

Hence number of buckets C will fill in 120 minutes = 2 * 6  =  12 buckets = 60 litres

Thus total water being fed to buckets by pipe A , B and C  =   100 + 80 + 60  =   240 litres

Hence this is nothing but the capacity of the tank..

Hence B) should be the correct option.

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