ArithmeticA can do a piece of work in 10 days and B can do in 20 days. In how many days they will finish the work together?

A can do a piece of work in 10 days and B can do in 20 days. In how many days they will finish the work together?

Solution: A and B both can do a work in

$\Rightarrow \frac{1}{10} + \frac{1}{20} \Rightarrow \frac{2 + 1}{20} = \frac{3}{20} \Rightarrow \frac{20}{3} d a y s$