A man completes 2/5 of a work in 8 days. If his work rate is doubled, how many more days will it take him to finish the remaining work?

Question: A man completes 2/5 of a work in 8 days. If his work rate is doubled, how many more days will it take him to finish the remaining work?

Solution:
2/5 of the work is done in = 8 days
∴ full work is done in = (8 × 5)/2 days
= 20 days

∴ His daily work rate = 1/20 per day

If his work rate is doubled, his new daily work rate is,
= (1/20) × 2 = 1/10 per day

Remaining portion of the job = 1 - (2/5)
= 3/5

Now,
1/10 work is done in = 1 day
∴ 3/5 work is done in = (3/5) ÷ (1/10) days
= (3/5) × 10
= 6 days

Therefore, it will take him 6 more days to finish the job.