Question

Elspeth knows that Pi times r almost-equals 9.42 centimeters. What would she need to do to find the circumference?

Answer 1

To find the circumference of a circle when given that \( \pi \times r \approx 9.42 \) centimeters, you can use the formula for the circumference:

\[
C = 2 \pi r
\]

Since you know that \( \pi r \approx 9.42 \), you can first express \( r \) in terms of this value:

\[
r \approx \frac{9.42}{\pi}
\]

Now that you have \( r \), you can find the circumference \( C \):

\[
C = 2 \pi r = 2 \times 9.42 \approx 18.84 \text{ centimeters}
\]

So, Elspeth can find the circumference by either:

1. Multiplying \( 9.42 \) by \( 2 \) to get \( 18.84 \) centimeters.
2. Or calculating \( C \) using \( r \) derived from \( \pi r \approx 9.42 \).

Thus, to obtain the circumference, Elspeth only needs to double \( 9.42 \) centimeters:

\[
C \approx 2 \times 9.42 = 18.84 \text{ centimeters}
\]