急~~~~math~~10點

1.不論圓的大小 , 圓周大約是直徑的( )倍 , 這個值叫做( ) .

Circumference (圓周) = Pi x Diameter (直徑) or 2 x Pi x Radius (半徑)
Pi = 3.142
Circumference = 3.142D or 6.284R

2.圓A的半徑是30cm , 圓形B的直徑都是30cm , 請問哪一個圓的面積比較大?大多少?兩圓的面積合起來又是多少 ?
Area of A = 3.142 x 30^2 = 2827.8cm2
Area of B = 3.142 x (30/2)^2 = 706.95cm2
Circle A is bigger than Circle B
Total Area of Circles = 2827.8 + 706.95 = 3534.75cm2

3.一個圓舷直徑變成原來的6倍 , 圓周長變成原來的幾倍 ?
Circumference, C=3.142D
If D1 is increased to 6D, C1=3.142 (6D) = 6 (3.142D) =6C
6 倍

4.甲圓直徑8cm , 乙圓半徑2cm , 甲圓的面積是乙圓我多少倍 ?
Area A = 3.142 x (8/2)^2 = 50.27cm2
Area B = 3.142 x (2)^2 = 12.57cm2
Area A/Area B = 50.27/12.57 = 4 倍

5.直徑10cm的圓形和邊長10cm的正方形 , 哪個面積比較大 ? 相差多少平方厘米 ?

Area of Circle = 3.142 x (10/2)^2 = 78.55cm2
Area of Square = 10x10 = 100cm2
Are of Square is Bigger than Area of Circle
Difference in Area = 100 - 78.55 = 21.45cm2

1)(唔肯定)3.14 圓周率
2)a 大一倍
30x2x3.14+30x3.14
=188.4+94.2
=282.6cm
(第三題唔know)
4)8/(2+2) {即係8除以(2+2)}
=2倍
5)相差:68.6cm
圓面積:10x3.14=31.4cm
正方形面積:10x10=100cm
所以正方形面積比較大