1) Equation that you need is:
C = 2πr
The diagram shows that the radius is 3.5, so plug it in the equation and solve for C
C = 2(3.14)(3.5)
C = 21.98
Rounded to tenth: 22.0
---
2) The equation you need to know here is:
A = πr²
The diagram shows diameter is 12, so radius is 6. Plus in the info, we have and solve for A
A = 3.14(6)²
A = 113.04
rounded to tenths: 113.0
---
3) Find the diameter of a circle with a circumference of 50mm.
C = 2πr
50 = 2(3.14)r
50 = 6.28r
r = 50 / 6.28
r = 7.96
You were asked to find the diameter, so double that, then round it to tenths:
d = 2r
d = 2(7.96)
d = 15.92
Rounded to 15.9mm