a , b and c can do a work in 15 , 20,45 days respectively . in how many days they can complete the work together .
lcm = 180 no of days = [ 180 / ( 180 / 15 + 180 / 20 + 180 / 45 ) = [ 180 / ( 12 + 9 + 4 ) ] = [ 180 / 25 ] = 7.2 days answer : e
inverse(add(inverse(add(add(add(add(const_2, const_3), 15), add(add(const_2, const_3), 15)), add(const_2, const_3))), add(inverse(15), inverse(add(add(const_2, const_3), 15)))))