Alek went for a walk. D(t) models the distance Alek walked (in kilometers) after t hours.
What does the statement D(0.5) < D(1) - D(0.5) mean?

a) The distance Alek walked during the first half-hour is shorter than the distance he walked during the following half-hour.
b) The distance Alek has walked after walking for an hour is greater than the distance he has walked after half an hour.
c) The time it took Alek to walk the first half kilometer is shorter than the time it took him to walk the following half kilometer.

The correct answer is option (a) The distance Alek walked during the first half-hour is shorter than the distance he walked during the following half hour.

Step-by-step explanation: The model used for his journey is given as D(t). This is the distance he walked after t hours. The variables here are the distance he has covered and the amount of time it took him.

However, the variables in the model has now been given as t = 0.5 and also t = 1.

These shows the time it took for Alek to cover a certain number of kilometres which are half an hour (0.5) and one hour  (1.0) respectively.

D(0.5) can now be translated as the distance he walked after half an hour, while D(1) - D(0.5) can be translated as the distance he walked after one hour minus half an hour.

Therefore the statement D(0.5) < D(1) - D(0.5) means;

The distance Alek walked during the first half-hour is shorter than (or less than) the distance he walked during the following half-hour.