It takes 12 men 8 hours a day to finish a piece of work in 4 days. In how many days will it take 4 men working 16 hours a day to complete the same piece of work?
6 days
8 days
10 days
12 days
Correct answer is A
12 men working 8 hours a day can complete the work in 4 days
12 men working 1 hour a day will complete the same work in (8 x 4) days [working less hours a day means they have to work for more days]
1 man working 1 hour a day will complete same work in (8 x 4 x 12) days [fewer number of men working means the remaining ones will have to work for more days ]
So, it will take 1 man working 1 hour a day to complete a piece of work in (8 x 4 x 12) days = 384 days
Now,
1 man working 16 hours a day will complete the piece of work in (384/16) days = 24 days [working more hours a day means less days to complete the work]
∴ 4 men working 16 hours a day will complete the piece of work in (24/4) days = 6 days [more men working means fewer days to complete the work]
ALTERNATIVELY
12 x 8 x 4 = 4 x 16 x d
⇒ d = \(\frac{12 \times 8 \times 4}{4 \times 16}\)
⇒ d = \(\frac{384}{64}\)
⇒ d = 6
∴ 4 men working 16 hours a day will complete the piece of work in 6 days
