The task is to generate the correct answer for a given math problem.

Q: Problem: two pipes a and b can separately fill a cistern in 60 minutes and 75 minutes respectively . there is a third pipe in the bottom of the cistern to empty it . if all the three pipes are simultaneously opened , then the cistern is full in 50 minutes . in how much time , the third pipe alone can empty the cistern ?

A: 100 min
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Q: Problem: the probability is 1 / 2 that a certain coin turns up heads on any given toss . if the coin is tossed 6 times , what is the probability that the coin turns up tails on at least one of the tosses ?

A: 63 / 64
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Q: Problem: a person borrows 9000 for 9 years at 3 % p . a . simple interest . he immediately lends it to another person at 7 % p . a . for 9 years . find his gain in the transaction per year .

A:
360
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