RRB Group-D Model Paper 15 with answers for online practice

Question : 11 of 100

Marks: +1, -0

A tap can empty a tank in 30 minutes. A second tap can empty it in 45 minutes .If both the taps operate simultaneously, how much time is needed to empty the tank?

30 min
18 min
14 min
15 min

Validate

Solution:

Given

1^{st}

tap can empty the tank in 30 minutes.
∴ In 1 min, it can empty 1/

30^{th}

part of tank

2^{nd}

can empty the tank in 45 min
∴ In 1 min it can empty 1/

45^{th}

part of the tank
Working together, in 1 min they can empty volume of tank = 1/30 + 1/45
⇒ Working together in 1 min they can empty volume of tank = 5/90 = 1/18 of the tank volume
∴ To empty the whole tank, time taken = 18 min

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