To solve for $c$ when $r = 5$ in the equation $c = 2 \pi r$:

1. Substitute $r = 5$ into the equation:

$c = 2 \pi \times 5$

2. Calculate:

$c = 10 \pi$

Using $\pi \approx 3.1416$:

$c = 10 \times 3.1416 = 31.416$

Rounding to 2 decimal places:

$c \approx 31.42$

So, the result is $c = 31.42$.

Would you like more details on this, or have any questions?

Here are 5 related questions:

1. How would the result change if $r = 10$?
2. What is the circumference formula for a circle?
3. Can you derive the formula $c = 2 \pi r$?
4. How is the value of $\pi$ determined?
5. How does the circumference relate to the diameter of a circle?

Tip: Always keep $\pi$ in your calculations until the final step to avoid rounding errors!