a , b , c can do a piece of work in 20 days , 30 days and 40 days respectively , working alone . how soon can the work be done if a is assisted by b and c on alternate days ?
"a + b 1 day work = 1 / 20 + 1 / 30 = 1 / 12 a + c 1 day work = 1 / 20 + 1 / 40 = 3 / 40 work done in 2 days = 1 / 12 + 3 / 40 = 19 / 120 19 / 120 work is done by a in 2 days whole work will be done in 2 * 19 / 120 = 3 days approximately answer is a"
divide(const_2, add(add(divide(const_1, 20), divide(const_1, 30)), add(divide(const_1, 20), divide(const_1, 40))))