A can do a piece of work in 12 days. B is 60 % more efficient to do the same work. If both of them work together then the number of days required to do the same work is
60 % more efficient, therefore total number of days required by him to do the complete work can be
obtained by the formula
12 *1 = 1.6 * x
=> x = 12 / 1.6 = 7.5
When both of them work together, the work of 1 day is (1/12) + (1/7.5) = 13/60
Hence total number of days required are 60/13