The circumference of the wheel can be expressed by:
\(circumference = 2 \pi r\)
Where r = the radius of the wheel.
Since the spoke reaches from the center of the wheel to its rim then r = length of the spoke
By rearranging the circumference equation we get:
\(r = \frac{circumference}{2 \pi }\)
If circumference = 42 inches then:
\(r = \frac{42}{2 \pi }\)
r = 6.68
Which is closest to B
Your book may have a typo in it as the answer to 4 decimal places is 6.6845 which rounds down to 6.68, not up to 6.69.
