A, B and C alone can finish a job in 20, 25 and 30 days, respectively. A and B together start doing the job. However, they leave it after 10 days. The remaining part of the job is finished by C alone. How many days did C take to finish the job ?
4 days
3 days
5 days
6 days
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC CISF-AC-EXE – 2023
– B’s daily work rate = 1/25 of the job.
– C’s daily work rate = 1/30 of the job.
– A and B work together for 10 days.
– Combined daily work rate of A and B = (1/20) + (1/25) = (5/100) + (4/100) = 9/100 of the job per day.
– Work done by A and B in 10 days = (9/100) * 10 = 90/100 = 9/10 of the job.
– Remaining part of the job = Total job – Work done by A and B = 1 – 9/10 = 1/10 of the job.
– C finishes the remaining 1/10 of the job alone.
– Time taken by C = Remaining work / C’s daily work rate.
– Time taken by C = (1/10) / (1/30) = (1/10) * 30 = 30/10 = 3 days.