a can do a work in 15 days and b in 20 days . if they work on it together for 4 days then the fraction of the work that is left is ?
"explanation : a ’ s one day work = 1 / 15 b ’ s one day work = 1 / 20 ( a + b ) ’ s one day work is = 1 / 15 + 1 / 20 = 7 / 60 their 4 days work = 4 x 7 / 60 = 7 / 15 remaining work = 8 / 15 answer : option d"
subtract(const_1, multiply(add(divide(const_1, 15), divide(const_1, 20)), 4))