Figure 1 shows a gear system used in a motorized conveyor belt.
An electric motor turns the large gear wheel. The teeth of the large gear wheel lock into the teeth of the small gear wheel, causing it to turn.

The large gear wheel has 45 teeth.
The small gear wheel has 15 teeth.
The large gear wheel turns 4 times each second.
Calculate the number of times that the small gear wheel turns each second.