Answer:
16% of students will complete the exam in less than 60 minutes
Step-by-step explanation:
The Empirical Rule(68-95-99.7) states that, for a normally distributed random variable:
68% of the measures are within 1 standard deviation of the mean.
95% of the measures are within 2 standard deviation of the mean.
99.7% of the measures are within 3 standard deviations of the mean.
In this problem, we have that:
Mean = 70
Standard deviation = 10
What percentage of students will complete the exam in less than 60 minutes
60 = 70-10
So 60 is one standard deviation below the mean
By the Empirical Rule, 68% of the measures are within 1 standard deviation of the mean, that is, from 60 to 80 minutes. The other 100-68 = 32% is outside this interval. Since the normal distribution is symmetric, 16% of those are below 60 and 16% of those are above 80.
16% of students will complete the exam in less than 60 minutes
