#### Tectonic plates are large segments of the Earth’s crust that move slowly. Suppose that one such plate has an average speed of 4.0 cm/year.

(a) What distance does it move in 1.0 s at this speed?

(b) What is its speed in kilometers per million years?

**Solution:**

**Part a**

We know that the formula for the distance traveled, d, if we are given rate, r, and time, t is given by

Therefore, the distance traveled is

Therefore, the distance traveled by the tectonic plate is about ☚

**Part b**

We need to convert 4.0 cm/year to km/My.

Therefore, the speed of the tectonic plates is 40 km/My. ☚