At any latitude, the Earth completes one rotation per day. 

At the equator, the circumference of the Earth is about 40000 km, so the speed of rotation is 40000 km/day or 463 m/s.

If you pick a line of higher latitude and look at it on a globe, you will see that the line of latitude is smaller than the equator. 

One rotation completed in a day is therefore a shorter distance; at 60 degrees latitude the line is about (cos 60 x 40000) = 20000 km long, so the speed of rotation is 20000 km/s or 230 m/s.