How many square meters does it take to make a cylindrical chimney with a bottom radius of 0.2m and a height of 15cm?

Question 1: How many square meters of iron sheets do you need to make a cylindrical chimney with a bottom radius of 0.2m and a height of 15cm?

Solution: The chimney has no bottom and cover, so only the side area of its cylinder is calculated, and then

Required iron sheet area

= transverse area Note: Expand the edge to get a rectangle.

= perimeter of bottom surface * cylinder height

= 2 * π * r *h

= 2 × 3. 14 × 0.2 × 0. 15

= 0. 1884 (m2)

The second question is how many square centimeters of iron sheet is needed to make a cylindrical oil drum with a bottom radius of 20 cm and a height of 40 cm? How many square decimetres?

Solution: Oil drums should only need the bottom area, without adding the top area.

Required iron sheet area

= bottom area × 1+ lateral area (only one bottom area is added, and no top area is needed, so it is not multiplied by 2).

= bottom area+bottom perimeter * column height

= π * r * r + 2 * π * r *h

= 3. 14 × 20 × 20 + 2 × 3. 14 × 20 × 40

= 1256 + 5024

= 6280 (square centimeter)

= 6280 × 0.0 1 = 62.8 (square decimeter)

= 6280 × 0.000 1 = 0.628 (m2)

The bottom diameter of the cylindrical ventilation pipe is16cm and the length is 10 decimeter. How many square decimetres of iron sheet do you need to make a ventilation duct like 10?

First, calculate the iron sheet required for a ventilation pipe, and then multiply it by 10 to get the answer.

Solution: The ventilation pipe has no two bottom surfaces of the cylinder, and we only need to calculate the side area of the cylinder.

Directly calculated by decimeter, 16cm = 1.6dm, then

Transverse area s of ventilation pipe

= perimeter of bottom surface * cylinder height

= π * d * h

= 3. 14 × 1.6 × 10

= 50.24 (square decimeter)

Therefore, the required iron sheet area = 10 × 50.24 = 502.4 (square decimeter).