ShmoopTube

Where Monty Python meets your 10th grade teacher.

Search Thousands of Shmoop Videos


Playlist Geometry and Measurement Test Questions 53 videos

0
SAT Math 1.1 Geometry and Measurement
719 Views

SAT Math 1.1 Geometry and Measurement. What is the circumference of the circle?

1
SAT Math 10.2 Geometry and Measurement
198 Views

SAT Math 10.2 Geometry and Measurement. How far does a point on the outside of the circle travel?

2
SAT Math 10.5 Geometry and Measurement
192 Views

SAT Math 10.5 Geometry and Measurement. How many rotations does each tire make?

See All

SAT Math 1.1 Geometry and Measurement 719 Views


Share It!


Description:

SAT Math 1.1 Geometry and Measurement. What is the circumference of the circle?

Language:
English Language

Transcript

00:03

Here’s a question that's part of a balanced Shmoopy breakfast.

00:06

A circle has an area of 100π cm2. What is the circumference of the circle?

00:13

And here are the potential answers...

00:16

All right…seems to us we’re going to have to know a formula or two to solve this puppy.

00:24

We should know that the area of a circle is πr2…

00:26

…and that the circumference of a circle is 2πr.

00:31

The problem has graciously told us the area, so we should be able to figure out what r is,

00:35

and then just plug ‘er into the circumference formula.

00:38

Okay…so by swapping out what we’re given with what we know…

00:41

…we get that 100π equals πr2.

00:44

We can divide pi out of both sides to give us 100 equals r squared…and then take the

00:48

square root of both sides to get r = 10.

00:51

All right, we can take our new r value and move it over to the circumference formula…

00:56

…which becomes 2 pi times 10…or 20 pi.

00:59

Which is answer D.

01:00

Wow…20 pi… that’s not just a pi… that’s a whole bakery.

Related Videos

SAT Math 2.1 Geometry and Measurement
2779 Views

SAT Math 2.1 Geometry and Measurement. What is the measure of angle z in terms of x and y?

SAT Math 9.4 Algebra and Functions
1300 Views

SAT Math 9.4 Algebra and Functions

SAT Math 9.2 Algebra and Functions
377 Views

SAT Math 9.2 Algebra and Functions

SAT Math: Identifying an Equation for the Average of Two Percentages
23 Views

In 2014, the unemployment rate of one county in California was 7%. In another county, the unemployment rate was 11%. Which of the following express...

SAT Math: Which Equation Represents Profit?
13 Views

Angela is making cookies for a bake sale. She expects each batch of her cookies to sell for $40. It costs her $10 to make one batch of cookies, and...