#Radius Of A Cylinder from Height and Surface Area

29 messages · Page 1 of 1 (latest)

safe thorn
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,rotate

stiff zealotBOT
safe thorn
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which one

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oh

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to work out SA you'd do area of curved + area of top and bottom circle right

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let radius be r

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so the areas of the two circles would be pir^2 + pir^2 = 2pir^2

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now the curved area can be rolled out into a rectangular sheet if that makes sense

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its length would be 20

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and the circumference of one of those circles is the width, which is 2pir

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curved area = 20 x 2pir = 40pir

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so now we can make an equation

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2pir^2 + 40pir = 300

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pir^2 + 20pir = 150

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divide by pi

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r^2 + 20r = 150/pi

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r^2 + 20r - 150/pi = 0

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solve for r and ur done

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r = 2.16 or -22.2

sage tide
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When you divided 300 by 2

safe thorn
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2

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yh

sage tide
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I didnt divide

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40pir

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By 2

safe thorn
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oh

sage tide
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Thanks for the help

sage tide