By which rule of thumb can you determine from the speed the distance in metres a motor vehicle travels in one second?

Answer 1 is correct because it’s a quick mental conversion from km/h to “meters per second,” which tells you how far the car travels in one second.

Rule of thumb: take the speed in km/h, divide by 10, then multiply by 3. This works because 1 km/h is about 0.28 m/s, and “÷10 ×3” approximates “÷3.6” (the exact conversion). It’s not perfectly exact, but it’s close enough for driving-theory safety calculations.

Example: 50 km/h → 50/10 = 5 → 5×3 = 15 meters in 1 second (exact would be about 13.9 m). 100 km/h → 100/10 = 10 → 10×3 = 30 meters (exact about 27.8 m).

Why this matters: it helps you estimate how far you travel during reaction time. If your reaction time is about 1 second, then at 100 km/h you’re already around 30 meters further before braking even starts, which is why higher speed quickly increases stopping distance.