180
xkcd #3248: 182.8 Meters
(imgs.xkcd.com)
Title text:
They rounded down to 182.8 instead of rounding up to 182.9 because 182.9 might make the statement incorrect.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3248/
If you've 24" tyres and a first gear ratio of 3.5:1, then:
RPM x (pi x 24" circumference )x (1/63360 miles per inch) x (60 minutes per hour) x (1/3.5 ratio) = 4.5 mph
Giving the RPM at a satisfyingly round 221.6 rpm.