instruction:
The task is to generate the correct answer for a given math problem.
question:
Problem: a man whose speed is 4.5 kmph in still water rows to a certain upstream point and back to the starting point in a river which flows at 1.5 kmph , find his average speed for the total journey ?
answer:
4


question:
Problem: a group of men decided to do a work in 55 days , but 15 of them became absent . if the rest of the group did the work in 60 days , find the original number of men ?
answer:
180


question:
Problem: how long does a train 100 m long travelling at 60 kmph takes to cross a bridge of 80 m in length ?
answer:

10.8 sec