Discussion

Explanation:

Let the time taken by A and B alone be ‘A’ and ‘B’ days respectively.

Together they can complete the work in 3 days.
⇒ $\frac{1}{A}+\frac{1}{B}=\frac{1}{3}$ …(1)

Now, they work for 2 days together and rest of the work is completed by A alone in 2 more day.

⇒ 1 = $\left(\frac{1}{A}+\frac{1}{B}\right)$ × 2 + $\frac{1}{A}$× 2

⇒ 1 = $\frac{1}{3}$× 2+ $\frac{1}{A}$× 2

⇒ $\frac{1}{3}$ = $\frac{2}{A}$

⇒ A = 3 days

Substituting this in (1), we get

B = 6 days.

Hence, option (b).

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