A, B and C can do a work in 15,20,45 days respectively. In how many days they can complete the work together.
Choices: A) 5.2 days B) 9.2 days C) 8.2 days D) 6.2 days E) 7.2 days

Rationale: lcm = 180 no of days = [ 180 / ( 180 / 15 + 180 / 20 + 180 / 45 ) = [ 180 / ( 12 + 9 + 4 ) ] = [ 180 / 25 ] = 7.2 days answer : e
Answer: E