Tick (✓) the correct answer:


Tick (✓) the correct answer:

A alone can do a piece of work in 10 days and B alone can do it in 15 days. In how many days will A and B together do the same work?

(a) 5 days

(b) 6 days

(c) 8 days

(d) 9 days


(b) 6 days

A can do a work in 10 days.

A's 1 day work $=\frac{1}{10}$

B can do a work in 15 days.

B's 1 day work $=\frac{1}{15}$

$(\mathrm{A}+\mathrm{B})$ 's 1 day work $=\frac{1}{10}+\frac{1}{15}=\frac{5}{30}=\frac{1}{6}$

$\mathrm{A}$ and $\mathrm{B}$ together will take 6 days to complete the work.

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