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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
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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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