Changing sped

If two meshing gear have the same number of teeth, they turn at the same speed, if the driving gear has more teeth than the driven gear, it will drive the driven gear faster. On the other hand, if the driven gear has more teeth, them it will be driven around more slowly. Gears that increase speed are called multiplying gears. Those reduce speed are reducing gears. Reducing gears are used in the transmission system of cars, for example (see page 47). When a car is traveling at about 55 mph (88 km/h), the wheels male about 750 revolutions per minute (rmp). A car engine turn at about 3,000 rmp. Q  what is the missing number in the following statement? The gears must reduce the speeds transmitted by a ratio of -:1.