a can do a job in 5 days and b can do it in 15 days . a and b working together will finish twice the amount of work in - - - - - - - days ?
"explanation : 1 / 5 + 1 / 15 = 4 / 15 = 4 / 15 15 / 4 = 15 / 4 * 2 = 7 ½ days answer : e"
add(divide(const_1, 5), divide(const_1, 15))