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A painting job can be completed by 5 painters in 12 days. If 5 more painters join the team 8 days after starting work on the job, then how many more days are required to complete the job?
Answer: 2
Solution:
Total effort required by 5 painters for 12 days = 5 × 12 = 60 man-days.
Initial effort by 5 painters for 8 days = 5 × 8 = 40 man-days.
Job still requires 60 − 40 = 20 man-days, and there are 10 painters available to do it.
Additional effort required by 10 painters for 20 man-days = 20 / 10 = 2 days.
Thus, 2 more days are required to complete the painting job.
Alternative Shorter Solution:
5 painters require 12 − 8 = 4 more days to complete the job.
Therefore, 5 + 5 = 10 painters will require 4 × 5 / 10 = 2 more days to complete the job.
Food for thought:
The number of days for the job is inversely proportional to the number of painters. So, is 'number of days × number of painters = constant'?
What assumptions were made to arrive at the solution?
Is something assumed about the output of the painters?
Try the Quiz : Puzzles & Brain Teasers : Painting Job
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