1. Check your understanding!
Practice Problems
Check your understanding!

2. Problem 1
What is the area of this circle? What is its circumference?

3. Answer
Its area is * r2. This is equal to * 52 = 25 ≈ 25 * 3.14 = 78.5 Its circumference is 2 r = 10 ≈ 31.4

4. Problem 2
What is the radius of this circle? What is its circumference?

5. Answer
By dividing the area by and taking the square root, we can find the radius of the circle. 314 / ≈ 100, so the radius is approximately the square root of 100, which is 10. Circumference = 2 r = 20 ≈ 62.8

6. Problem 3
The diameter of this circle is 5x+3, and the circumference is
(4x+5). What is the value of x?

7. Answer
We know that the formula for the circumference of a circle is Circumference = * diameter. Thus, we have (5x+3) = (4x+5) 5x + 3 = 4x + 5 x = 2 Thus, the diameter is 13 and the circumference is 13 .