can a car be sold with a broken odometer?
Anyone can sell a car with a broken odometer legally by disclosing in the bill of sale that the "true mileage is unknown". Contact your local DMV - some states (I believe California is one of them) which forbids any car to be sold, or operated without a functioning odometer.
There may be a broken gear inside the odometer.
100 miles.
Depends on what the odometer reads and which region the car is to be sold/bought in.
My speedometer works and the odometer does not because there is a plastic gear in the odometer that is broken.
Depends on the state where the car is being sold. It is against the law to sell a vehicle in most states without notifying the buyer in writing that the odometer does not work and the mileage is unverifiable. It is also illegal in some states to even sell a vehicle with an inoperable odometer.
The odometer measures the distance the car has travelled.
likely on the back of the odometer, it depends on the car. You can likely find out by calling the car manufacturer
Because your odometer, or something connecting the odometer to the battery, is broken. Most likely the odometer is the problem if the rest of your dashboard is working fine.
The odometer is broken and needs replaced.
You cannot reset the odometer in your car, however you can reset your trip odometer.
Tire size may be off. Previous owner might have turned it back to improve the value of the car. It might be broken. IT might have been broken eariler and replaced with a unit from another car of another mileage.