a can do a piece of work 20 days . b can do work in 35 days . in how many days they will complete the work together ?
"lcm = 140 , ratio = 20 : 35 = 4 : 7 no of days = 140 / ( 4 + 7 ) = 90 / 5 = 12.72 days answer : c"
divide(const_1, add(divide(const_1, 20), divide(const_1, 35)))