In a factory, there are two machines A and B. A machine can produce 1000 watts power in 5 hours and by running both the machines together can produce same watts power in 3 hours. Find the time taken by B machine alone to produce same watts of power. a) 5 hrs b) 7 hrs & 30 mins c) 6 hrs d) 6 hrs & 30 mins
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b) 7 hrs & 30 mins
Explanation:
A type machine can produce 1000 watts power in 5 hours.
Then A's 1 hour work = 1/5.
Both A and B can produce in 3 hours.
And 1 hour work of (A + B)'s = 1/3.
B's 1 hour work = 1/3 = 1/5 = 2/15.
Therefore, machine B can produce 1000 watts power in 15/2 hours.
i.e., 15/2 hours = 7.5 hours = 7 hours and 30 minutes.