Question 828845

If the student finished at the mean, that means 50% of the students finished in less than 40 minutes and 50% of the students finished greater than 40 minutes.
Finishing in 48 minutes is the mean plus one standard deviation so the probability is greater than 50%. 
From the answers above, only one answer works. 
Usually it's not that simple.  
Looking at a normal distribution curve at 1 standard deviation greater than the mean, the cumulative probability is 0.841 or 84.1%.