Anoop and Bhanu together can finish a certain piece of work in 90 days, while Bhanu and Charu together can complete the work in 70 days. Bhanu, Charu, and Danny together can finish the work in 42 days. In how many days can Anoop alone complete 40% of the work if Danny is 20% more efficient than Charu?

ATQ, Let Anoop, Bhanu, Charu and Danny can be defined as A, B, C and D respectively. Let the total work be 630 units. (LCM of 90, 70 and 42) Amount of work done by A and B together in one day = 630/90 = 7 units Amount of work done by B and C together in one day = 630/70 = 9 units Amount of work done by B, C and D together in one day = 630/42 = 15 units Amount of work done by D alone in one day = 15 – 9 = 6 units Amount of work done by C alone in one day = 6/1.20 = 5 units Amount of work done by B alone in one day = 9 – 5 = 4 units Amount of work done by A alone in one day = 7 – 4 = 3 units Time taken by A alone to complete 40% work = 0.40 × 630/3 = 84 days