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F.2 Maths (in hurry!)Thanks a lot!

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The surface area A of a sphere is given by the formula A =4兀r^2where r is the radius of the spherea) Find the value of A hwen i) 兀=3.14 and r=1 ii) 兀=22/7 and r=3.5b)Make r^2 the subject of the formulac) Find the value of r for each of the following values of Ai) 36兀ii) 196兀*I want clear steps . Thanks... 顯示更多 The surface area A of a sphere is given by the formula A =4兀r^2 where r is the radius of the sphere a) Find the value of A hwen i) 兀=3.14 and r=1 ii) 兀=22/7 and r=3.5 b)Make r^2 the subject of the formula c) Find the value of r for each of the following values of A i) 36兀 ii) 196兀 *I want clear steps . Thanks a lot . Who is the the best i will give (10x2=20marks)

最佳解答:

a1) Area=4 X 3.14 X 1X1=12.56 a2)Area=4 X 22/7 X 3.5 X 3.5=154 b) A=4兀r^2 r^2=A/4兀 c1) r^2=A/4兀 Now A=36兀 , So r^2=36兀/4兀 r^2=9 r=3 c2) r^2=A/4兀 Now A=196兀 , So r^2=196兀/4兀 r^2=49 r=7

其他解答:

a) i) A = 4(3.14)1^2 = 25.12 ii) A = 4(22/7)(3.5)^2 = 157 b) A =4兀r^2 r^2 = 4兀/A c) i) A =36兀 4兀r^2 = 36兀 r^2 = 9 r = 3 ii) A = 196兀 4兀r^2 = 196兀 r^2 = 49 r = 7|||||ai) A= 4(3.14)(1^2) = 12.56 aii) A= 4(22/7)(3.5^2) or A= 4(22/7)(3.5^2) = 88/7 x 12.25 = (22/7)(7^2) = 154 = 22 x 7 = 154 b) A = 4兀r^2 A/4兀= (4兀r^2)/4兀 r^2= A/4兀 ci) r^2=36兀/4兀 r^2=9 r=3 cii) r^2=196兀/4兀 r^2=49 r=7 2006-10-17 22:20:31 補充: sorry for the question (aii)it isA= 4(22/7)(3.5^2)= 88/7 x 12.25 = 154 orA= 4(22/7)(3.5^2)= (22/7)(7^2)= 22 x 7= 154
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