A) 15
B) 20
C) 25
D) 30
Correct Answer: C
Solution :
Suppose, B alone can do the same work in x days. Then, \[\frac{1}{x-5}+\frac{1}{x}=\frac{9}{100}\] \[\Rightarrow \] \[\frac{x+x-5}{x\,\,(x-5)}=\frac{9}{100}\] \[\Rightarrow \] \[\frac{2x-5}{{{x}^{2}}-5x}=\frac{9}{100}\] \[\Rightarrow \] \[9{{x}^{2}}-245x+500=0\] \[\Rightarrow \] \[9{{x}^{2}}-225x-20x+500=0\] \[\Rightarrow \] \[9x\,\,(x-25)-20\,\,(x-25)=0\] \[\Rightarrow \] \[x=\frac{20}{9}\]or 25 \[\therefore \]B alone can do the same work in 25 days.You need to login to perform this action.
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