You are travelling at 40 km/h. The braking distance for evasive braking is approximately 8 metres. How long is the braking distance at 50 km/h given otherwise the same conditions?

Braking distance doesn’t rise in a straight line with speed; it rises roughly with the square of the speed. A good rule of thumb for “evasive/emergency braking” in German theory questions is: braking distance is proportional to (speed)², so a small increase in speed causes a noticeably larger braking distance.

From 40 km/h to 50 km/h, the speed factor is 50/40 = 1.25. Squaring that gives 1.25² = 1.5625. So the braking distance becomes 8 m × 1.5625 ≈ 12.5 m. That’s why answer 1 is correct.

How to remember it for similar questions: if speed increases by 25%, braking distance increases by about 56%. And if speed doubles, braking distance becomes about four times as long (under the same conditions).