Xiao Gang and Xiao Liang collected some cans. The tank bottom is 8cm in diameter and 15cm in height. A * * * has collected one hundred cans. How many square meters of aluminum skin do you need to make these cans?

8×3. 14× 15+(8÷2)? ×3. 14×2=477.28cm？

477.28× 100=47728cm？ =4.7728m？

2. Build a cylindrical reservoir with a bottom diameter of10m and a depth of 2.2m.. How many square meters is this reservoir? If cement is plastered around and at the bottom, what is the plastering area?

Floor space: (10÷2)? ×3. 14=78.5m？ ;

Cement plastering area = 78.5+10× 3.14× 2.2 =147.58m?

3. A cylindrical iron drum without a cover has a bottom circumference of 65,438+02.56 decimeters and a height of 5 decimeters. How many decimetres of tin does it take to make such a barrel?

Bottom radius =12.56 ÷ 3.14 ÷ 2 = 2dm;

Need: 12.56×5+2? ×3. 14=75.36dm？

4. A biscuit box without a lid, with a bottom radius of 7 cm and a surface area of 1406.72 square decimeter, find the height of this biscuit box.

( 1406.72-7? ×3. 14)÷(7×2×3. 14)

=28.5