Question

The cylinder has a height of 1.2m, radius 0.4m and is open at the top. The inside surface is painted at a cost of $2.30 per m.2.
Calculate the cost of painting the inside surface.

Answer 1

The cylinder has a height of 1.2m, radius 0.4m and is open at the top. The inside surface is painted at a cost of $2.30 per m.2.

Calculate the cost of painting the inside surface.

Write a surface area of cylinder:

$$A = 2 \pi r ^ {2} + 2 \pi r h = 2 \pi r (r + h).$$

Write formula without top:

$$A = \pi r ^ {2} + 2 \pi r h$$ $$\pi 0. 4 ^ {2} + 2 \pi \cdot 0. 4 1. 2 = 3. 5 1 9$$

Calculate cost of painting:

\mathrm{Cost} = 2.3 * 3.519 = 8.09$

Answer: 8$ 9c.