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Question
If 12 pumps can empty a reservoir in 20 hours, then time required by 45 such pumps to empty the same reservoir is ______ hours.
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Solution
If 12 pumps can empty a reservoir in 20 hours, then time required by 45 such pumps to empty the same reservoir is 5h 20 min hours.
Explanation:
∵ 12 pumps can empty a reservoir in 20 h.
∴ 1 pump can empty in 20 × 12 i.e. 240 h.
Then, 45 pumps can empty the same reservoir in
`240/45 h = (240 xx 60)/45 min` ...[∵ 1 h = 60 min]
= `14400/45`
= 320 min
= 5 × 60 + 20
= 5h 20 min
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