By which rule of thumb can you determine the braking distance in metres from speed when braking normally?

The correct rule of thumb to estimate the braking distance in meters during normal braking is to take your speed in km/h, divide it by 10, and then square that number. For example, if you are driving at 50 km/h, you divide 50 by 10 to get 5, and then multiply 5 by 5, which equals 25 meters. This means your braking distance is approximately 25 meters. This formula reflects that braking distance increases with the square of speed, so if you double your speed, your braking distance roughly quadruples. This is an important concept for safe driving and understanding stopping distances.