Tick (✓) the correct answer:


Tick (✓) the correct answer:

A can do a piece of work in 20 days which B alone can do in 12 days. B worked at it for 9 days. A can finish the remaining work in

(a) 3 days

(b) 5 days

(c) 7 days

(d) 11 days


(b) 5 days

A can complete the work in 20 days.

Work done by A in 1 day $=\frac{1}{20}$

B can complete the work in 12 days.

Work done by B in 1 day $=\frac{1}{12}$

In 9 days, B completes $\frac{9}{12}$, i.e., $\frac{3}{4}$ of the work and leaves $1-\frac{3}{4}$, i. e., $\frac{1}{4}$ of the work undone.

$\therefore$ Time taken by $\mathrm{A}=\frac{1}{4} \div \frac{1}{20}=\frac{1}{4} \times 20=5$ days

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