statistics
posted by karla .
John drives to work each morning and the trip takes an average of = 38 minutes. The distribution of driving times is approximately normal with a standard deviation of = 5 minutes. For a randomly selected morning, what is the probability that John's drive to work will take between 36 and 40 minutes?

Use zscores.
Find two zscores using this formula:
z = (x  mean)/sd
Mean = 38
Sd = 5
Use 36 for x to determine first zscore.
Use 40 for x to determine second zscore.
Once you have both zscores, check a ztable for the probability between the two scores.
I hope this will help get you started.