RRB NTPC Mains or Stage 2 Model Paper 6 with solutions

Question : 36 of 119

Marks: +1, -0

4 pipes can fill a reservoir in 15, 20, 30 and 60 hours respectively. The first was opened at 6 am, second at 7 am third at 8 am and fourth at 9 am. When will the reservoir be full ?

11 am
12 pm
12.30 pm
1.00 pm

Validate

Solution:

(d) Let the time be t hours after 6 am.

∴1/15× t+{(t -1)}/20+{ (t -2)}/ 30+{(t -3)}/ 60

∴4t + 3 (t – 1) + 2 (t – 2) + (t – 3) = 60
∴t = 7 hours ∴It is filled at 1 pm

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