0.8米,前轮滚动一周,压路的面积是多少平方米?
3.14×0.8×1.6 = 2.512×1.6 = 4.0192(平方米)
答:前轮滚动一周,压路的面积是4.0192平方米。
综合练习:
❖ 3 张师傅要做一个半径为2.5米,高3米的圆柱形铁皮烟囱。 他大约需要多少平方米的铁皮?(得数保留整数)
3.14×2.5×2×1.8 = 3.14×9 = 28.26 ≈29(平方米) 答:他大约需要29平方米的铁皮。
• 14、Thank you very much for taking me with you on that splendid outing to London. It was the first time that I had seen the Tower or any of the other famous sights. If I'd gone alone, I couldn't have seen nearly as much, because I wouldn't have known my way about.
=50.24(平方分米)
例题教学:
❖ 例2
❖ 一种圆柱形状的罐头,它的底面直径是11 ❖ 厘米,高是15厘米。侧面有一张商标纸(如下
图),商标纸的面积大约是多少平方厘米?(接 头处忽略不计)
动手实践:
❖ 圆柱侧面积计算公式的推导:
(1)想一想并同桌讨论:怎样求圆柱的侧面积? (2)动一动,验证你的想法。 (3)说一说方法和思路是否正确。 (4)算一算看结果是否基本一致。
圆柱的侧面积
❖ 重点:计算公式的推导 ❖ 难点:计算公式的应用
准备活动:
❖ 复习: 1、口算: 3.14×2= 6.28 3.14×4=12.56 3.14×6= 18.84 3.14×8= 25.12 3.14×10= 31.4 3.14×0.5= 1.57