2.① 3. 14× 5× 8 = 125.6 cm2。
② 3. 14× (40× 2 )× 20 = 50.24 cm2， 15 cm = 0. 15 m。
3. 14×0. 15×4 = 1.884 m2 4， 1.8×3.5×4 = 25.2 m2 25.2×0.5 = 12.6kg。
Page 18 Answer 1, (1) Height of the bottom perimeter (2) 7838+0.50080.000000000085
2. Bottom area: 3.14× (2.5÷ 2) 2× 2 = 9.8125m2. Side area: 3.14× 2.5× 4 = 31.4m2..
Surface area: 9.8125+31.4 = 41.2125m3,3.14× (2× 2.
3.14×10×10 = 314 m2 62.8× 6 ~ 314 = 690.8 m2 690.8× 3 = 2072.4 kg.
Page 19 answer 1, lateral area surface area 187.92 square centimeters 94.2 square centimeters 2565.2 square decimeters 79 1.28 square decimeters 3452. 16 square meters 854.08 square meters 2,3./kloc.
Side area: 3.14× 6×1.5 = 28.26m2, 28.26+56.52 m2, 4.15.7 ÷ 3.14 ÷ 2 = 2.5.
3. 14× 2.52× 2 = 39.25 cm2
15.7× 15.7 = 246.49 cm2 39.25-246.49 = 285.74 cm2 5， 10 ÷ 2 = 5 cm。
3. 1 4× 52+40×10+3.14×10× 40 ÷ 2 =1106.5cm2 Page 20 Answer/
2，3. 14 × (0.2 ÷ 2) 2× 3 = 0.0942 m3，40 ÷ 2 = 20 cm。
3.14× 202× 60 = 75,360 cubic centimeters = 75.36 liters; 75.36 liters < 80 liters; It can't hold 80 liters.
4.3.14×10×10 = 314 square centimeter 5024 ÷ 3 14 = 16 cm 5,5× 8× 7.8 =
Page 265438 +0 Answer
1，① 8 ÷ 2 = 4cm
3.14× 42× 6 = 3010.44 cubic centimeter 23.14× 52× 9 = 706.5 cubic meters ②, 6÷2 = 3cm.
3. 14× 32× 10 = 282.6 cm3 = 282.6 ml 3. 14× 22× 2.5 = 3 1.4 m31.4× 50.
3. 14× 42 = 50.24 m2 25.12 ÷ 50.24 = 0.5m.
Page 22 answer
1, ① surface area: 345.4 cm2 Volume: 47 1 cm3 ② surface area: 40 1.92 cm2 Volume: 602.88 m3.