a can do a work in 9 days and b can do the same work in 18 days . if they work together , in how many days will they complete the work ?
one day ' s work of a and b = 1 / 9 + 1 / 8 = ( 2 + 1 ) / 18 = 1 / 6 so , the time taken to complete the work is 6 days . answer : a
divide(const_1, add(divide(const_1, 9), divide(const_1, 18)))