ShmoopTube

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Here’s your shmoop du jour, brought to you by formulas.

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The number one choice of race car drivers and babies.

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A cylinder 10 feet long and with a radius of 4.5 feet needs to be painted on all surfaces.

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One can of paint will cover 20 square feet.

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How many cans are needed?

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Here are the potential answers...

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We’re not sure what we did to deserve this cruel and unusual punishment…

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…but we must have done SOMETHING to be charged with this community service project.

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This one’s pretty simple…all we need is to know the formula for the surface area of a cylinder.

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The formula in question is 2 pi r squared plus length times pi 2r…

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…then we can just plug in our radius of 4.5 and our length of 10.

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We need to now see what our calculator has to say about it.

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It comes out to 409.77.

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We know that one can of paint will cover 20 square feet…

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…so we take 409.77 and divide it by 20 to get 20 point…something.

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Doesn’t really matter what comes after the decimal point, because we’re going to have to round up…

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...we need a whole other can of paint. Right?

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The answer is 21 cans and that's choice B…and we’re done.

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