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

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

Geometry and Measurement | Measurement (Linear, Area, Three-Dimensional) |

Mathematics and Statistics Assessment | Measurement (Linear, Area, Three-Dimensional) |

Product Type | TSI |

TSI | Mathematics and Statistics Assessment TSI Math TSI Mathematics |

TSI Math | Geometry and Measurement |

TSI Mathematics | Geometry and Measurement |

Test Prep | TSI |

### Transcript

the perfect consolation prize for a wrong solution And the

perfect prize for a correct solution Yeah win win Anyway

this example asked us to find the diameter of the

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

the area of a circle directly to its diameter But

there is another way here Use the formula for the

area of a circle Find the radius and then double

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

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

give us a lot of this fifteen point nine square

inches is pi r squared or well we can divide

out pie on both sides That gets us a five

in change and inches there for r squared Take square

root of five point o six and we get a

two point two five inches as the radius Well now

that we have the radius the cookie find the diameter

by just multiplying it by two And that gets us

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

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