When the teacher tells us the answer, let's think about it first and fill in the relevant words

When the teacher tells us the answer, let's think about it first and fill in the relevant words

Instead of waiting for the teacher to tell us the answer, let's think about it first
Hope to adopt, O (∩)_ Thank you

Fill in the appropriate words: () constantly temper children, () can let children learn to be independent

Only ability

No matter how reasonable you are, you shouldn't hit people

No matter how reasonable you are, you shouldn't hit people

A piece of circular iron sheet has an inner radius of 30 decimeters and a ring width of 40 decimeters. How many square decimeters is its area?

Annular area = outer circle inner circle π≈ 3.14
(30+40)²π-30²π
=(4900-900)π
=4000π
=12560 (square decimeter)
A: it covers an area of 12560 square decimeters

A circular iron sheet, the outer diameter is 6 decimeters, the inner radius is 2 decimeters, its area is______ Square decimeter

3.14 × [(6 △ 2) 2-22], = 3.14 × 5, = 15.7 (square decimeter); answer: the area of this iron sheet is 15.7 square decimeter

The diameter of a circular iron sheet is 8 decimeters and the width of the ring is 2 decimeters. How many square decimeters is the area of this circular iron sheet?

8/2=4dm
4-2=2dm
3.14*4*4-3.14*2*2
=50.24-12.56
=37.68 (square decimeter)

The outer radius of a ring iron sheet is 40 cm and the ring width is 10 cm. How many square centimeters is the area of the ring iron sheet?

40-10 = 30 (CM) 3.14 × (402-302) = 3.14 × (1600-900) = 3.14 × 700 = 2198 (square cm); answer: the area of this ring iron sheet is 2198 square cm

A ring, outer diameter 6 decimeters. Ring width 1 decimeter, ring area is () square decimeters

Outer circle radius 6 △ 2 = 3
Then the radius of small circle is 3-1 = 2
3.14×3×3-3.14×2×2=15.7
The area of the ring is (15.7) square decimeters

For a ring, the diameter of the inner circle is 2 decimeters, the width of the ring is 1 decimeter, and the area of the ring is 1______ ．

2 △ 2 = 1 (decimeter), 1 + 1 = 2 (decimeter), 3.14 × 22-3.14 × 12 = 3.14 × (4-1), = 3.14 × 3, = 9.42 (square decimeter); answer: the area of the ring is 9.42 square decimeter; so the answer is: 9.42 square decimeter

A circular iron sheet, the outer diameter is 6 decimeters, the inner radius is 2 decimeters, its area is______ Square decimeter

3.14 × [(6 △ 2) 2-22], = 3.14 × 5, = 15.7 (square decimeter); answer: the area of this iron sheet is 15.7 square decimeter