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Q)

A is thrice as good a workman as B and therefore is able to finish a job in 30 days less than B. How many days will they take to finishthe job working together?

**[Railways 2007]**

Explanation

Let A take a and B take 3a days to finish the work.

As per the question,

3a-a=30

${\therefore}{}{\mathrm{x}}{=}\frac{30}{2}{=}{15}{}{\mathrm{days}}$

Time taken by B to complete the work is 3a

So 3×15=45 days

Therefore 1 day work of (A+B)= $\frac{1}{15}+\frac{1}{45}=\frac{3+1}{45}=\frac{4}{45}$

Hence, (A+B) will finish the work in $\frac{45}{4}\mathrm{or}11\frac{1}{4}\mathrm{days}$

**Hence option C is correct**

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