1. Given that the radius of a semicircle is 8 cm, find the area and perimeter.

Solution: The bisector of S=8 π =200.96 (square centimeter).

C=(8×2)×π=50.24 (cm)

There is a round flower bed in Xingguang Primary School. The perimeter of the flower bed is 25. 12m. What is the floor area of this flower bed? ×××

Solution: r = 25. 12 \u 2 = 4(m)

The square of s = 4×π = 50.24 (m2)

3. How many times can a copper wire with a length of 1570 be wound around a circular coil with a radius of 2.5cm?

Solution: 1570(2.5×2×π)

= 1570÷ 15.7

= 100 (circle)

4. Cut the disc with a rectangular iron sheet with a length of 10 cm and a width of 6 cm. The radius of the disc is 1.5 cm. How many can I cut at most?

Solution: 6÷( 1.5×2)=2.

10( 1.5×2)≈3 (approximate value of tail cutting method)

2×3=6

A: You can cut up to 6 pieces.

The echo wall of Beijing Tiantan Park is a world-famous acoustic miracle, and it is a circular wall. The perimeter of the fence is about 204.7 meters. What is its diameter and area respectively? (The number shall be kept to one decimal place)

6. Build a road with a width of 1 meter outside the circular flower bed with a diameter of 8 meters. How much floor tile area does it take to lay the path?

Solution: 8÷2=4 4+ 1=5.

(5 squared -4 squared) ×π=9×π=28.26

7. The wheel radius of a car is 0.3m Can this wheel cross a bridge with a length of 1800m after rolling for 1000 cycles?

(0.3×2)×π= 1.884 (m)

1.884×1000 =1884 (m)

Because 1884 > 1800

So I crossed a bridge with a length of 1800 meters.