Question
Pipe ‘A’ can fill a tank in 25 hours while pipe
‘B’ can empty it in 30 hours. They were operated on alternate hours starting with pipe ‘A’. Find the percentage of tank filled this way in 42 hours.Solution
Let the total capacity of tank be 150 units Efficiency of pipe ‘A’ = 150/25 = 6 units/hour Efficiency of pipe ‘B’ = 150/30 = 5 units/hour Tank filled in 2 hours = (6 – 5) = 1 units Therefore, tank filled in (2 × 21 = 42 hours) = 1 × 21 = 21 units Required percentage of tank filled = (21/150) × 100 = 14%
The average age of 23 children and their teacher's age are 21 years. If the teacher's age is excluded, the average reduces by 1. What is the teacher's age?
32 × 15 + 60% of 200 = ? + 120
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