A semicircular flowerbed, its radius is 5cm, its perimeter is how many meters?

A semicircular flowerbed, its radius is 5cm, its perimeter is how many meters?

3.14 × 5 × 2 △ 2 + 5 × 2, = 15.7 + 10, = 25.7 (m), a: the circumference of the semicircular flower bed is 25.7 M

The circumference of a circle solves the problem
The outside diameter of a car tire is 1.02 meters
1. How many meters is the turning distance of the wheel? (accurate to 0.1 meter)
2. If the average speed is 335 cycles per minute, how many kilometers does the car travel per minute?
There is a big clock in the station hall. Its minute hand is 40 cm long. How many meters does this minute hand travel day and night?
Don't say anything when answering TT. I haven't learned that yet

1 3.1415926*1.02=3.2
2 3.2 * 335 = 1072m = 1.072km
3 0.4*2*3.1415926*24=30.16

On the circumference or area of a circle
1. A big clock, its minute hand is 40 cm long. How many cm does the tip of the minute hand travel when it rotates for a week?
2. When passing through a bridge, a wheel with a diameter of 1.2m needs to turn 500 turns. How long is the bridge?
3. Calculate the area of the shadow in the figure below. (unit: cm)
4. A ring with a width of 2 cm and a diameter of 1 decimeter. What is the area of the ring?
5. For a log, the perimeter of its cross section is 62.8 cm, find their cross section area
3. Calculate the area of the shadow in the figure below. (unit: cm)

1.40*2*3.14=251.2cm
2.1.2*3.14*500=188.4m
3.4/2=2cm
3.14*2*2=12.56cm2
12.56/2=6.28cm2
6.28*4=25.12cm2
4.1dm=10cm
10-2=8cm
3.14*(10*10-8*8)
=3.14*36
=113.04cm2
5.62.8/3.14/2=10cm
3.14*10*10=314cm2

It is known that the side area of the cone is 16 π CM & # 178;, and the center angle of the side expanded view is 90 ° to calculate the generatrix length

Cone side area = n / 360 × π × R & # 178; = 1 / 2lr (n refers to degree, l refers to arc length)
The formula r = 8 can be obtained from the formula of cone side area = n / 360 × π × R & # 178
Then calculate L, according to the formula of cone side area = 1 / 2lr, obtain L = 4

If the side view of a cone is a sector with an angle of 216 ° and an area of 60 π, then the height of the cone is______ ．

Let the length of generatrix be r, the radius of the bottom circle be r, s sector = 216 π × r2360 = 60 π, the solution is r = 10, the circumference of the bottom circle is 216 π × R180 = 12 π = 2 π R, the solution is r = 6, and the height of the cone is 102 − 62 = 8

If the bottom area of a cone is 1 / 3 of the side area, then the degree of the center angle of the cone in the expanded side view is

78

If the side area of the cone is 3 / 4 of the total area, find the center angle of the expanded side view of the cone

Base radius r, generatrix length L, center angle θ
θ=360*（R/L）
S side area = π LR
S base area = π R * r
S side area: s bottom area = 3:1
R/L=1/3
θ=360*（R/L）
=360/3
=120 degrees
That's it!

Given that the center angle of a cone is 90 degrees, the ratio of the bottom radius of the cone to the length of the generatrix is 0

It's 1 to 4

When the generatrix length of a cone is 10 cm and the area of the side view is 60 π cm2, the radius of the bottom of the cone is 0______ cm．

Let the radius of the bottom surface be r, 60 π = π R × 10, and the solution is r = 6cm

It is known that the radius of cone bottom is 10 cm and the length of generatrix is 40 cm

The solution is n = 90 ° and the cone surface area is π × 10 ^ 2 + π × 10 × 40 = 500 π cm ^ 2