Answer: d) 0.31
Step-by-step explanation:
Given : In a health club, research shows that on average, patrons spend an average of 42.5 minutes on the treadmill, with a standard deviation of 5.4 minutes.
i.e. and
It is assumed that this is a normally distributed variable.
Let x denotes the time spend by a person on treadmill.
Then, the probability that randomly selected individual would spent between 30 and 40 minutes on the treadmill.
Hence, the required probability = 0.31
Thus , the correct answer = d) 0.31