Question
There are two inlet pipes 'M', 'N' and one outlet pipe 'O'
in a tank. ‘M’ and ‘N’ can fill the tank in 12 minutes and 6 minutes respectively. ‘O’ is 50% less efficient than ‘M’. If ‘M’ and ‘O’ are open together but after 6 minutes ‘M’ is replaced with ‘N’, find the total time required to fill the tank completely.Solution
Tank = 12x units (LCM of 12 and 6)
M = x, N = 2x, O = 0.5x
6 mins: (x - 0.5x) × 6 = 3x
Remaining = 12x - 3x = 9x
Net = 2x - 0.5x = 1.5x
Time = 9x / 1.5x = 6 minutes
Total time = 6 + 6 = 12 minutes
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