While working 7 hour a day, A alone can complete a piece of work in 6 days and B alone in 8 days. In what time would they complete it together, 8 hour a day?
A. 3 days
B. 4 days
C. 2.1 days
D. 3.6 days
Answer: Option A
Solution(By Examveda Team)
A can complete the work in 7 × 6 = 42 hours 1 hour's work of A = $$\frac{1}{{42}}$$ B can complete the work in 7 × 8 = 56 hours 1 hour's work of B = $$\frac{1}{{56}}$$ (A + B)'s 1 hour's work $$\eqalign{ & = \frac{1}{{42}} + \frac{1}{{56}} \cr & = \frac{{4 + 3}}{{168}} \cr & = \frac{7}{{168}} \cr} $$∴ Time taken by (A + B) working 8 hours daily
$$\frac{{168}}{{7 \times 8}} = 3\,{\text{days}}$$
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Comments ( 3 )
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Thanks
1/42+1/56=7/168*8=7/21
3 days.
A+B 1 hour work is 1/42+1/56
see the solution