ShmoopTube

00:03

Here's the shmoopiest question you've likely heard in the last ten minutes...

00:07

Snow White just ran into an old woman who baked her an entire apple pie. How lucky is she?

00:12

The pie has a radius of 8 inches.

00:15

SW knows she can consume a mini-pie with a radius of 4 inches in five minutes.

00:20

At this rate, how long will it take her to consume the pie from the old hag?

00:24

The area of a circle, remember, is A equals pi times radius squared...

00:29

And here are the potential answers...

00:31

Before we spoil the ending, hit pause and try it yourself.

00:34

This question is asking us to derive the area of a circle from a formula...

00:38

...and then apply that derivation to a rate-of-eating problem.

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So... first, the question gives us the area of a circle formula -- pi times radius squared.

00:48

We first have to calculate the area of the first 4 inch pie and then the 8 incher.

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Pi-r squared of the first gives us 3.14 times r squared which is 16 or about 50;

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And pi-r squared of the second gives us 3.14 times 8 squared which is 64 or about 200.

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Now we can set up a ratio.

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50 square inches takes 5 minutes; so 200 square inches should take... how many minutes?

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Well, check out the ratio here. We have four times the square inchage, so...

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...we should also have 4 times the... time.

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Or, 20 minutes. Answer C.

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