X and Y can complete a project in 20 and 12 days, respectively. X began working alone, but after four days, Y joined him and worked with him until the job was completed. What was the duration of the project?
A. 6 days
B. 10 days
C. 15 days
D. 20 days
Answer:B
X and Y can complete a project in 20 and 12 days, respectively. X began working alone, but after four days, Y joined him and worked with him until the job was completed. What was the duration of the project?
A. 6 days B. 10 days C. 15 days D. 20 days
Explanation: Work completed by X in 4 days = 1/20 x 4 = 1/5Work remaining = 1 - 1/5 = 4/5.1 day's labour for (X + Y) = 1/20 + 1/12 = 8/60 = 2/15X and Y now complete 2/15 of the job in a single day.As a result, X and Y will complete four tasks in 15/5 x 4/2 = 6/5 days.As a result, the total time required = (6 + 4) days = 10 days.