a can do a job in 10 days and b can do it in 30 days . a and b working together will finish twice the amount of work in - - - - - - - days ?
"explanation : 1 / 10 + 1 / 30 = 4 / 30 = 2 / 15 15 / 2 = 15 / 2 * 2 = 15 days answer : d"
add(divide(const_1, 10), divide(const_1, 30))