You are travelling at 50 km/h, have a reaction time of 1 second, and brake normally. What is the stopping distance according to the rule of thumb?

The stopping distance in this situation is calculated using the rule of thumb for normal braking: you add the reaction distance to the braking distance.

The reaction distance at 50 km/h is calculated as follows: (Speed in km/h divided by 10) times 3.
So, 50 divided by 10 equals 5, times 3 is 15 meters.

The braking distance at 50 km/h (normal braking) is: (Speed in km/h divided by 10) squared.
So, 50 divided by 10 is 5, squared is 25 meters.

Add both together: 15 meters (reaction) + 25 meters (braking) = 40 meters total stopping distance.

Therefore, selecting 40 meters is correct. Remember this calculation method for similar questions about stopping distances.