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Math March 2 nd
1. If a metal cylinder with a bottom diameter of 20 cm and a height of 10 cm is completely immersed in a cylindrical water tank with a diameter of 40 cm, how many centimeters will the water surface of the water tank rise?

The radius of the bottom surface of the metal cylinder is

20 ÷ 2 = 10 cm

The volume of the metal cylinder is

10×10× 3.14×10 = 3140 cubic centimeters.

The radius of the bottom surface of the cylindrical water tank is

40 ÷ 2 = 20 cm

The bottom area of cylindrical storage tank is

20× 20× 3. 14 = 1256 cm2

The water level in the sink will rise.

3 140/ 1256 = 2.5cm。

2. Dig a cylindrical pool, and measure the bottom circumference of 3 1.4m and the depth of 2.4m from the inside. How many square meters is its inner wall and bottom covered with cement? How many tons of water can this pool hold? (There is no water weight of one cubic meter 1 ton)

The bottom radius is

31.4÷ 3.14÷ 2 = 5m.

The bottom area is

5× 5× 3. 14 = 78.5 square meters

The transverse area is

3 1.4× 2.4 = 75.36 square meters

The area covered by cement is

78.5+75.36 = 153.86 m2

This pool can hold water.

78.5× 2.4× 1 = 188.4 tons