Time and Work Important trick

This is again a very important question asked in many aptitude exams

Two men undertake to do a piece of work for Rs 1400. First man alone can do this work in 7 days while the second man alone can do this work in 8 days. If they working together complete this work in 3 days with the help of a boy, how should money be divided?

So funda is money is divided according to work performed  so first man in 3 days will be able to do 3/7 of work in 3 days o 3/7 of 1400 is   Rs 600

 Second man can do 3/8 of work in 3 days 3/8 of 1400 is  Rs 525

and rest money should be given to boy  1400-600 -525= Rs 275