Rohan can paint
Question:

Rohan can paint $\frac{1}{3}$ of a painting in 6 days. How many days will he take to complete the painting?

Solution:

Rohan can paint $\frac{1}{3} \mathrm{rd}$ of a painting in 6 days.

$\therefore$ Time taken by Rohan to complete the painting $=(6 \times 3)$ days $=18$ days.