00:00: Let's review how to find the area of a circle. Typically, if you're trying to find the area of a circle, you will be given the radius. So for this circle, suppose that the radius is 3 centimeters. Now, when you wanna find the area, you use a very famous formula for circles, which is that the area is equal to the number pi times r squared. And r stands for the radius, which we've been told in this situation is three. Pi is a number that is impossible to represent using just decimals, so what we do is approximate it with 3.14. In reality, that decimal goes on forever, but we use 3.14 for most of our calculations, 'cause it's close enough. 00:56: So in this situation, the area of the circle would be equal to pi which is 3.14 times r squared. Well, remember, r is three and three to the second power is the same as three times three, or nine. So our final answer is going to be nine times 3.14, and we can work that out using multiplication. Nine times four is 36. Nine times one is nine plus three is 12. Nine times three is 27 plus one is 28. But remember, we had two decimal places to the right of the point in this number, pi, so we have to put those back into the final answer. We get a final answer for the area of 28.26. One thing to watch out for when you do these problems is sometimes you will not be given the radius directly, but you might be given the diameter. Remember, the diameter is twice the radius. So if you're given, say, that the diameter is 12 inches, then when you go to do the calculation, you're gonna have to remember to cut that diameter in half and use, in this case, the radius, which would be just 6 inches.

Question

00:00: Let's review how to find the area of a circle. Typically, if you're trying to find the area of a circle, you will be given the radius. So for this circle, suppose that the radius is 3 centimeters. Now, when you wanna find the area, you use a very famous formula for circles, which is that the area is equal to the number pi times r squared. And r stands for the radius, which we've been told in this situation is three. Pi is a number that is impossible to represent using just decimals, so what we do is approximate it with 3.14. In reality, that decimal goes on forever, but we use 3.14 for most of our calculations, 'cause it's close enough. 00:56: So in this situation, the area of the circle would be equal to pi which is 3.14 times r squared. Well, remember, r is three and three to the second power is the same as three times three, or nine. So our final answer is going to be nine times 3.14, and we can work that out using multiplication. Nine times four is 36. Nine times one is nine plus three is 12. Nine times three is 27 plus one is 28. But remember, we had two decimal places to the right of the point in this number, pi, so we have to put those back into the final answer. We get a final answer for the area of 28.26. One thing to watch out for when you do these problems is sometimes you will not be given the radius directly, but you might be given the diameter. Remember, the diameter is twice the radius. So if you're given, say, that the diameter is 12 inches, then when you go to do the calculation, you're gonna have to remember to cut that diameter in half and use, in this case, the radius, which would be just 6 inches.

Close
Question 1
The diameter of a circle is the radius multiplied by ___.
Responses
A 22
B 33
C 44
Question 2
If a circle has radius 3, you find the area by multiplying π by ____.
Responses
A 66
B 99
Question 3
A circle with radius 3 has an area of _____.
Responses
A 24.8824.88
B 26.3226.32
C 28.26

Answer 1

Question 1:

The diameter of a circle is the radius multiplied by __.
Correct Response: A) 22

Question 2:
If a circle has radius 3, you find the area by multiplying π by ____.
Correct Response: B) 9

Question 3:
A circle with radius 3 has an area of _____.
Correct Response: C) 28.26