A can lay railway track between two given stations in 16 days and B can do the same job in 12 days. With help of C, they did the job in 4 days only. Then, C alone can do the job in:
A. $$9\frac{1}{5}$$ days
B. $$9\frac{2}{7}$$ days
C. $$9\frac{3}{5}$$ days
D. 10
Answer: Option C
Solution(By Examveda Team)
$$\eqalign{ & \left( {{\text{A + B + C}}} \right){\text{'s}}\,{\text{1}}\,{\text{day's}}\,{\text{work}} = \frac{1}{4} \cr & {\text{A's}}\,{\text{1}}\,{\text{day's}}\,{\text{work}} = \frac{1}{{16}} \cr & {\text{B's}}\,{\text{1}}\,{\text{day's}}\,{\text{work}} = \frac{1}{{12}} \cr & \therefore {\text{C's}}\,{\text{1}}\,{\text{day's}}\,{\text{work}} \cr & = \frac{1}{4} - \left( {\frac{1}{{16}} + \frac{1}{{12}}} \right) = {\frac{1}{4} - \frac{7}{{48}}} = \frac{5}{{48}} \cr & {\text{So,}}\,{\text{C}}\,\,{\text{alone}}\,{\text{can}}\,{\text{do}}\,{\text{the}}\,{\text{work}}\,{\text{in}} \cr & \frac{{48}}{5} = 9\frac{3}{5}\,{\text{days}} \cr} $$Join The Discussion
Comments ( 4 )
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please tell when the answer is 5/48 then why you done reciprocal please tell it please please
7 is the addition of 3 and 4 in the numerator.
How to came in 7/48, 48 means LCM iunderstood but 7 means what pls explain
can i solve this question by LCM then how..?