Curved Surface area of a right circular cylinder

Q.

The curved surface of a cylindrical bulb of height $18cm$ and base radius $7cm$ is to be painted in luminating gold colour such that ${\frac{2}{3}}^{rd}$ of the height of the bulb emits golden light; painting is done at ₹ 5 per sq. cm. The cost of painting the bulb is_____.
$(use\pi =\frac{22}{7})$

1. ₹ 2640

2. ₹ 1650

3. ₹ 2750

4. ₹ 2800

Q. The radii of two right circular cylinder are in the ratio $2:3$ and their height are in the ratio $5:4$. Calculate the ratio of their volumes.