instruction:
The task is to generate the correct answer for a given math problem.
question:
Problem: the average weight of a , b and c is 60 kg . if the average weight of a and b be 70 kg and that of b and c be 50 kg , then the weight of b is :
answer:
60 kg

question:
Problem: a train running at the speed of 70 km / hr crosses a pole in 9 sec . what is the length of the train ?
answer:
175 m

question:
Problem: pipe a fills a tank of capacity 800 liters at the rate of 40 liters a minute . another pipe b fills the same tank at the rate of 30 liters a minute . a pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute . if pipe a is kept open for a minute and then closed and pipe b is open for a minute and then closed and then pipe c is open for a minute and then closed and the cycle is repeated , when will the tank be full ?
answer:
48 minutes