trigonometry
posted by y912f .
assuming that Earth's radius is 6400 km, find the linear velocity of Quito, Equador, a city on the equator. (Use pi=3.1416 and 1.6 km=1 mile).

I guess we are to do miles per hour ?
v = omega * r
omega = 2 pi /24 hr
r = 6.4*10^3 km (1 mile/1.6 km) = 4,000 miles
so
v = 4000 miles (2 pi/ 24 hr)
=3333 miles/ hour 
(2 pi * 6400 km)/(24 hours)
That will give you the answer in km/h. Divide by 1.6 for miles per hour.
Actually, a better conversion factor with five significant figures is 1.6093 km/mile
It makes no sense to have five significant figures for pi and only two for the kmtomiles factor 
my choices are
2094.4 mph
209.4 mph
1047.2 mph
104.7 mph 
LOL  the textbook writer is using a calculator with pi on it but not the unit conversions :)

v = 4000 miles (2 pi/ 24 hr)
=1047.2 miles/ hour 
thnks