Ratios and Pi

Which of the following formulas do we use to find the Circumference of a circle when given the radius?

• $C\ =\ \pi d$

• $C\ =\ 2\pi r$

• $A\ =\ \pi r^2$

• $C\ =\ \pi r^2$

Which of these best describes  $\pi?$  

• The square root of the area of a circle.

• The ratio of the radius of a circle to its diameter.

• The radius of a circle times 3.14. 

• The ratio of the circumference of a circle to its diameter.

Which of the following equations represents the relationship between the circumference, C, and the diameter, d, of any circle?

• $C\ =\ \pi r$

• $Cd\ =\pi$

• $\pi=\ \frac{C}{r}$

• $\pi=\frac{C}{d}$

What number is pi?

• 1.41

• 3.14

• 2

• 5.14

Which of these ratios is the closest approximation of pi?

• $\frac{13}{4}$

• $\frac{19}{6}$

• $\frac{16}{5}$

• $\frac{22}{7}$

_______________ is the distance around a circle.

• circumference

• radius

• center

• diameter

_____________ is half of the diameter

• circumference

• radius

• center

• diameter

______________ is twice the radius

• circumference

• radius

• center

• diameter

If the radius of a circle is 12.5 meters, the diameter is _

• 6.25 meters

• 25 meters

• 125 meters

• 50 meters

If the diameter of a circle is 50 yards, the radius is ______.

• 100 yards

• 150 yards

• 25 yards

• 15 yards