A) 49
B) 7
C) 6
D) 42
Correct Answer: A
Solution :
[a] Let the time taken by boy to complete the work \[=4x\]day Similarly, the time taken by woman to complete the work\[=2x\]days The time taken by man to complete the work \[=x\] days [\[\therefore \]A woman is twice efficient than a boy and a man is twice efficient than woman] Now, together they can complete the work in 7 days. So, \[\frac{1}{4x}+\frac{1}{2x}+\frac{1}{x}=\frac{1}{7}\] [One day's work of all working together] \[\frac{1+2+4}{4x}=\frac{1}{7};\frac{7}{4x}=\frac{1}{7}\] \[\Rightarrow \] \[x=\frac{49}{4}\] \[\therefore \]A boy can finish the work in \[4\times \frac{49}{4}=49\]days |
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