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TSI Math: Working Backwards from a Circle's Area to Find Its Diameter 20 Views


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Description:

If the area of a circular cookie is 15.9 square inches, how much does it measure across?


Transcript

00:03

All right sy shmoop there's Another one for you If

00:05

the area of a circular cookie is fifteen point nine

00:08

square inches while big cookie how much does it measure

00:12

across Yeah That's A texas size cookie Okay well cookies

00:18

The perfect canvas for math problems That's Because cookies are

00:21

the perfect consolation prize for a wrong solution And the

00:24

perfect prize for a correct solution Yeah win win Anyway

00:27

this example asked us to find the diameter of the

00:30

cookie with a given area There's no formula that links

00:32

the area of a circle directly to its diameter But

00:35

there is another way here Use the formula for the

00:37

area of a circle Find the radius and then double

00:41

it So let's start by finding the radius a equals

00:43

pi r squared Remember that's the formula there So they

00:45

give us a lot of this fifteen point nine square

00:48

inches is pi r squared or well we can divide

00:52

out pie on both sides That gets us a five

00:55

in change and inches there for r squared Take square

00:58

root of five point o six and we get a

01:00

two point two five inches as the radius Well now

01:03

that we have the radius the cookie find the diameter

01:06

by just multiplying it by two And that gets us

01:08

You have four and a half inches So that's what

01:10

This Cookie measures The answer is d and we're schmuck 00:01:14.031 --> [endTime] because we eat our cookies Thank you very much

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