john completes a piece of work in 320 days , rose completes the same work in 480 days . if both of them work together , then the number of days required to complete the work is ?
"if a can complete a work in x days and b can complete the same work in y days , then , both of them together can complete the work in x y / x + y days . that is , the required no . of days = 320 × 480 / 800 = 192 days answer is b"
divide(const_1, add(divide(const_1, 320), divide(const_1, 480)))