The radius of sector AOB is 12cm, and the angle AOB is 120 degrees. The length of arc AB (the result is accurate to 0.1cm) and the area of sector AOB (the result is accurate to 0.1 square centimeter) are calculated

The radius of sector AOB is 12cm, and the angle AOB is 120 degrees. The length of arc AB (the result is accurate to 0.1cm) and the area of sector AOB (the result is accurate to 0.1 square centimeter) are calculated

The length of arc AB = 3.14 × 12 × 2 × 120 / 360 = 25.12 (CM) ≈ 25.1 (CM)
The area of sector AOB = 3.14 × 12 & # 178; × 120 / 360 = 150.72 (cm2) ≈ 150.7 (cm2)

1. As shown in the figure on the right, the radius of the sector AOB is 12cm, ∠ AOB = 120 ° and the arc length and area of the sector are calculated
2. There is a metal cylinder, which is completely immersed in a cylindrical glass with a bottom diameter of 10cm and a height of 20cm. The diameter of the metal cylinder is 4cm and the height is 5cm. Now, how much will the water surface of the glass be reduced if the metal cylinder is fished out of the water? (regardless of water loss)
3. A store increases the purchase price of a certain brand of DVD by 35%, and then advertises "20% discount for customers". As a result, each DVD can still make a profit of 116 yuan. How much is the purchase price of each DVD? (equation)

π * 12 * 2 * (120 / 360) = 8 π cm arc length
12 * 12 * π * (120 / 360) = 48 π square centimeter area
π*2*2*5/(π*5*5)＝0.8cm
(1+35%)x*0.8-x=116
1.08x-x=116
x=1450

Cut a sector with a center angle of 288 degrees from a circular iron sheet with a radius of 5cm
The volume of a conical container made of this fan-shaped sheet iron is 50.24 cubic centimeters. How high is the cone?

Arc length of sector = circumference of cone bottom = (288 ° / 360 °) × 2 × 3.14 × 5 = 25.12 (CM) radius of cone bottom = 25.12 ／ 2 ／ 3.14 = 4 (CM) area of cone bottom = 3.14 × 4 & # 178; = 50.24 (square cm) height of cone = (3 × volume of cone) ／ area of cone bottom = (3 × 50.24) ／ 50.24 = 3