a can do a job in 15 days and b in 30 days . if they work on it together for 4 days , then the fraction of the work that is left is ?
"a ' s 1 day work = 1 / 15 b ' s 1 day work = 1 / 30 a + b 1 day work = 1 / 15 + 1 / 30 = 3 / 30 = 1 / 10 a + b 4 days work = 1 / 10 * 4 = 2 / 5 remaining work = 1 - 2 / 5 = 3 / 5 answer is b"
subtract(const_1, multiply(4, add(divide(const_1, 15), divide(const_1, 30))))