Raj can do a piece of work in 20 days. He started the work and left after some days, when 25% work was done. After it Abhijit joined and completed it working for 10 days. In how many days Raj and Abhijit can do the complete work, working together?

Explanation:-

Efficiency of Raj = $$\frac{{100}}{{20}}$$ = 5%
Work completed by Raj = 25%
Rest work = 75%
Efficiency of Abhijit = $$\frac{{75}}{{10}}$$ = 7.5%
Combined efficiency = 5 + 7.5 = 12.5%
They will complete the whole work by working together in,
= $$\frac{{100}}{{12.5}}$$ = 8 days