Question

a can do 2/3 of a certain work in 12 days and b can do 1/6 of the same work in 4 days. both a and b can complete the work in

Answer 1

That means 'a' requires 18 days to finish the complete work and 'b' requires 24 days to finish the same work. If they work together, they finish the work in following number of days:

$\frac{1}{\frac{1}{18}+\frac{1}{24}} = \frac{1}{\frac{7}{72}} = \frac{72}{7} days$