Rebuilding Any Row From Scratch

Tables get forgotten; methods don't. And exams don't restrict themselves to the five speeds a table happens to list.

For any speed, at the 1.5-second reaction this table assumes:

1. Reaction: drop the last digit × reaction time × 3. (At 70 km/h: 7 × 1.5 × 3 ≈ 31 m)
2. Braking (dry): drop the last digit, square it, × 0.4. (7² × 0.4 ≈ 20 m)
3. Wet: double the braking figure. (≈ 39 m)
4. Add. (70 km/h ≈ 51 m dry, 70 m wet)

Thirty seconds of arithmetic reproduces any row of this lesson — which is the real thing this lesson wants you to own. The table is a convenience; the method is the knowledge.