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When a circle is enlarged, its area is eight times larger and its circumference is 50.24 cm larger than before. What is the original area of the circle? It's better not to use the equation. It can't be used,
The area is 8 times more than the original, that is, it becomes 9 times of the original (according to the square relation of the formula), so the diameter becomes 3 times and the perimeter becomes 3 times, so the original perimeter is 25.12cm, so the original area is 50.24cm
There is a semicircular part, the perimeter is 20.56, find the area of this semicircular part
Radius 20.56 △ 3.14 + 2 = 4
Area 3.14 × 4 × 4 / 2 = 25.12
An annular iron sheet has an outer radius of 5 decimeters and an inner diameter of 6 decimeters. What is the area of the annular iron sheet
Radius of inner circle = 6 △ 2 = 3 decimeters
Area = 5 × 5 × 3.14-3 × 3.14 = 50.24 square decimeters
A circular iron sheet has an outer radius of 7 cm and an inner radius of 0.5 decimeter. What is the area of the circular iron sheet?
7 = 0.7 decimeter, 3.14 × (0.72-0.52), = 3.14 × (0.49-0.25), = 3.14 × 0.24, = 0.7536 square decimeter. A: the area of this ring is 0.7536 square decimeter
The outer circumference of a ring is 18.84 decimeters, and the inner circumference is 6.28 decimeters. The area of the ring is () square decimeters, and the width of the ring is () decimeters?
Outer circle radius = 18.84 △ 3.14 △ 2 = 3 (decimeter)
Outer circle area = 3.14 × 3 & # 178; = 28.26 (square decimeter)
Inner circle radius = 6.28 △ 3.14 △ 2 = 1 (decimeter)
Inner circle area = 3.14 × 1 & # 178; = 3.14 (square decimeter)
Area of ring = 28.26-3.14 = 25.12 (square decimeter)
Ring width = 3-1 = 2 (decimeter)
There is a ring-shaped object with an outer circumference of 18.84dm and an inner circumference of 12.56dm. How many square decimeters is the area of the object?
The outer circle radius is: 18.84 ÷ (2x3.14) = 3 (DM)
The inner circle radius is: 12.56 ÷ (2x3.14) = 2 (DM)
Ring area: 3.14x (3x3-2x2) = 15.7 (square decimeter)
A circle with a radius of 3 decimeters, if the radius is increased by 1 decimeter, then the circumference is increased______ Decimeter, area increased______ Square decimeter
Later, the radius of the circle: 3 + 1 = 4 (decimeter), perimeter increase: 2 × 3.14 × 4-2 × 3.14 × 3, = 6.28 × 4-6.28 × 3, = 25.12-18.84, = 6.28 (decimeter); area increase: 3.14 × 42-3.14 × 32, = 50.24-28.26, = 21.98 (square decimeter); answer: perimeter increase: 6.28 decimeter, face
For a circle with a radius of 2 decimeters, if the radius is increased by 1 decimeter, then the perimeter is increased by () decimeter, and the area is increased by () square decimeter?
Perimeter increase: 2 (2 + 1) π - 2 * 2 π = 2 π (decimeter)
Area increase: π (2 + 1) square - π 2 square = 5 π (square decimeter)
For a circle with a radius of 1 decimeter, if the radius increases by 1 decimeter, the perimeter increases by? Decimeter, and the area increases by? Square decimeter
Perimeter increase: 2 × (1 + 1) × 3.14-2 × 1 × 3.14 = 6.28 decimeters
Area increase: 3.14 × (1 + 1) &# 178; - 3.14 × 1 &# 178; = 9.42 square decimeters
For a circle with a radius of 4 decimeters, if the radius is increased by 1 decimeter, how much is the perimeter increased and how many square decimeters is the area increased
For a circle with a radius of 4 decimeters, if the radius is increased by 1 decimeter, the perimeter will be increased by 6.28 decimeters and the area will be increased by 28.26 square decimeters
2×3.14×（4+1-1）=6.28
3.14×（（4+1）²-4²）=28.26
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