Question

A can do a piece of work in 14 days while B can do it in 21 days .they began together and worked for 7 days.then, A fell I'll and B had to complete the work .in how many days was the work completed.

Answer 1

a's 1day work =1/14
b's 1 day work=1/21
ab's 1 day work =1/7
1/14 + 1/21 - 1/7
lcm = 42
6-5/42
=1/42
=42 days