The diameter of a circle is 6 decimeters. If its diameter increases by 4 decimeters, its perimeter increases by () decimeters, and its area increases by () square decimeters

The diameter of a circle is 6 decimeters. If its diameter increases by 4 decimeters, its perimeter increases by () decimeters, and its area increases by () square decimeters

Perimeter increase:
3.14 × 4 = 12.56 (decimeter)
Area increase:
3.14 × 4 × 4 = 50.24 (square decimeter)
The diameter of a circle is 6 decimeters. If its diameter increases by 4 decimeters, its perimeter increases by (12.56) decimeters, and its area increases by (50.24) square decimeters

When the radius of a circle is enlarged, its area increases 8 times and its perimeter increases by 25.12 decimeters. How many square decimeters is the original area of the circle?

According to the square of the area ratio is the length ratio, the radius is three times of the original. The perimeter is three times of the original, and the perimeter is increased by 25.12 decimeters, increased by two times. The original perimeter is 25.12 △ 2 = 12.56 decimeters, because 2 × radius × 3.14 = perimeter = 12.56, so the original half

A ring has an inner radius of 3 decimeters and an outer radius of 5 decimeters. How many square decimeters is the area of the ring?

3.14 × (52-32), = 3.14 × (25-9), = 3.14 × 16, = 50.24 (square decimeter). A: the area of this ring is 50.24 square decimeter

A cylindrical tin bucket without a cover has a circumference of 12.56 decimeters at the bottom and a height of 6 decimeters. How many square decimeters of tin do you need to make this bucket
(keep the whole number of TENS)

S = 12.56 * 6 + 3.14 * (12.56 / 2 / 3.14) ^ 2 = 90 square decimeter

The perimeter of the bottom area of a square iron water tank without cover is 24dm. How many square decibels of iron do you need to make such a water tank? The second question I wrote is 216 square decibels
Why did the teacher criticize me for being wrong

Tin water tank without cover cube
To make such a tank, you only need to make five surfaces, and you get six
Of course not
24 △ 4 = 6 decimeters
Iron sheet required: 6 × 6 × 5
=36×5
=180 square decimeters
Answer to do such a water tank to use 180 square decimeters of iron sheet

The perimeter of the bottom surface of a square iron water tank without a cover is 24 decimeters. How many liters of water can this water tank hold? How many square decimeters of iron sheet do you need to make such a water tank?

24 △ 4 = 6 (decimeter), 6 × 6 × 6 = 216 (cubic decimeter) = 216 (liter), 6 × 6 × 5 = 180 (square decimeter); answer: this water tank can hold 216 liters of water, so it needs 180 square decimeters of iron sheet to make such a water tank

The circumference of the bottom surface of a cylinder iron tank is 12.56 decimeters, and the height is 1 meter. How many square decimeters of iron sheet does it need to make such a tank?

According to the side area = bottom perimeter * height
1 meter = 10 decimeters
Side area: 12.56 * 10 = 125.6 (square decimeter)
Bottom circular radius: 12.56/3.14/2 = 2 (decimeter)
Bottom area: 2 * 2 * 3.14 = 12.56 (square decimeter)
Iron sheet area: 12.56 * 2 + 125.6 = 150.72 (square decimeter)
I told you according to the normal format. Choose me

The perimeter of the bottom surface of a cube fuel tank is 12 decimeters, and the area of the bottom of the tank is how many square decimeters. How many square decimeters of iron sheet should be used to make the fuel tank?
If the weight of diesel oil is 0.85 kg, how many kg diesel oil can this tank hold at most

Side length of bottom surface = 12 △ 4 = 3 (decimeter)
Bottom area = 3 × 3 = 9 (square decimeter)
Required iron sheet area = 9 × 6 = 54 (square decimeter)
Volume = 9 × 3 = 27 (cubic decimeter)
Diesel oil capacity = 27 × 0.85 = 22.95 (kg)

A cuboid with a cube at the bottom, 36dm in circumference, has a side area of 180 square decimeters?

36 △ 4 = 9 decimeters
180 △ 36 = 5 decimeters
5 × 9 × 4 + 9 × 9 × 2 = 342 square decimeters

The bottom of a rectangular tin box is a square with a circumference of 20 decimeters. What is the area of antirust paint on the outside of the tank? If the weight of each liter of gasoline is 0.68 kg, how many kg of gasoline can the tank hold at most?

20 divided by 4 equals 5 decimeters, and the volume is multiplied by 0,68