A) 4 days
B) 3 days
C) 2 days
D) 5 days
Correct Answer: B
Solution :
(b): A takes \[7\times 9=63\]hrs to complete 1 work. B takes \[6\times 7=42\]hrs to complete 1 work. \[8\frac{2}{5}=\frac{42}{5}\] hrs. In 1 hr, A does \[\frac{1}{63}\]work. In 1 hr, B does \[\frac{1}{42}\] work. Together (A+B) in 1 hr, do \[\frac{1}{63}+\frac{1}{42}=\frac{2+3}{126}\]\[=\frac{5}{126}\]work. Let them take 'x' days \[\therefore \]Total spent hrs \[=\frac{42}{5}*x=\frac{42x}{5}\] (A+B) together take \[\frac{126}{5}\]hrs to complete 1 work \[\Rightarrow \frac{42x}{5}=\frac{126}{5}\Rightarrow x=3\,days\]
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