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### Question

A can do a piece of work in 14 days. B is 40% more efficient than A. In how many days will they complete the work if they work together?

**A**

$5{5/6}$ days.

**B**

6 days.

**C**

$6{1/6}$ days.

**D**

$6{1/3}$ days.

**Soln.**

**Ans: a**

Let us first calculate the one day work of B. One day work of A is given as $1/14$. If B is 40% efficient, then one day work of B is $1/14$ × $140/100$ = $1/10$. Putting x = 14 and y = 10 in the shortcut method, we get ${xy}/{x + y}$ = ${35/6}$, which is same as: $5{5/6}$.