Efficiency of A is 40% more than B and B takes 21 days to complete a piece of work. A started the work alone and then B joined him 6 days before actual completion of the work. For how many days A worked alone?

Explanation

Efficiency Ratio = A : B = 140 : 100 = 7 : 5 Days Ratio = A : B = 5 : 7 B takes 21 days to complete a piece of work. => 7’s = 21 => 1’s = 3 => 5’s = 15 So A can complete the work in 15 days. Total units of work = 105 (LCM of 15,21) A = 7 unit B = 5 unit A and B worked for 6 days = 6 × (7+5) = 72 units Remaining work = 105 – 72 = 33 units Hence, A worked alone for = 33/7 days. IBPS RRB Scale I 2021 Prelims Memory Based Paper