2.4×2.4×3. 14×2+2.4×2×3. 14×4

=36. 1728+60.288

=96.4608

2. Licun will dig a cylindrical swamp with a bottom radius of 5 meters and a depth of 2 meters.

(1) How many square meters does this swamp cover?

5×5×3. 14=78.5 square meters

(2) spread cement on the side and bottom of the swamp. What is the area of cement?

5×2×3. 14×2+78.5

=62.8+78.5

= 14 1.3m2。

(3) What is the size of this swamp?

78.5×2= 157 cubic meters

3. A cylindrical steel with an area of 80 cm and a bottom radius of 6 cm. If steel weighs 7.8g per cubic centimeter, how much did this piece weigh just now?

6×6×3. 14×80×7.8 = 70536.96g。

4. How many cubic centimeters is a roll with a diameter of 1.5 and a height of 6 cm? Reserved integer

1.5÷2 = 0.75 cm.

0.75× 0.75× 3.14× 6 =10.5975 ≈11cubic centimeter.