Originally posted by shagadelic1892:
Another cheap-labour question but slightly more difficult
A and B working together can complete a job in 10 days. B and C
working together can complete the job in 15 days. A and C working
together can complete the job in 12 days. How many days would it
take A, B and C working together to complete the job?
Here's my solution:
For A and B, fraction of job completed each day = 1/10 => A + B
= 1/10
For B and C, fraction of job completed each day = 1/15 => B + C
= 1/15
For A and C, fraction of job completed each day = 1/12 => A + C
= 1/12
Next, add up the 3 equations and we have:
2A + 2B + 2C = 1/4 => A + B + C = 1/8
This equation implies that A, B and C working together can complete
1/8 of the job in one day.
Hence, no. of days required for A, B and C working together to
complete the job = 8
