(1) The surface area of a cylinder plus two bottom areas is the surface area. The bottom area of a cylinder is 20 square centimeters, and that of lateral area is 80 square centimeters. The surface area of this cylinder is 120 centimeters?

(2) When the formula for calculating the volume of a cylinder is derived, the cylinder is transformed into a cuboid.

③ The volume of a cylinder is 6 cubic decimeters, and the volume of a cone with the same base and height is 2dm?

Solve the problem:

1. Put a fish tail into a water tank with a length of 1 m and a width of 80 cm, and the water level will rise from 30 cm to 32 cm. Find the volume of this fish tail.

1m = 100cm；

? Volume of fish tail =100× 80× (32-30) =16000 cm?

2. The steel casing is 3m long, 20cm in outer diameter and 2cm in wall thickness. According to 1 cubic centimeter weighing 7.8 grams, how many kilograms does this steel pipe weigh? (Keep the whole number of kilograms)

Outer diameter = 20 ÷ 2 =10cm;

Inner diameter =10-2 = 8cm;

3m = 300cm

( 10? -8? )×3. 14×300×7.8

=36×3. 14×300×7.8

= 2645 13.6g

About 265 kilograms