The time (X) to complete a standardized exam is approximately normal with a mean of 70 minutes and standard deviation of 10 minutes. How much time should be given to complete the exam so that 80% of the students will complete the exam in the time given?

77.88 minutes

Step-by-step explanation:

Given that :

Mean (m) = 70

Standard deviation (s) = 10

For 80% of student to complete the exam. In the given time

Using the formula :

Zscore = (X - mean) / standard deviation

80th percentile = 80/100 = 0.8 has a Zscore = 0.7881

0.7881 = (X - 70) /10

0.7881 * 10 = X - 70

7.881 = X - 70

7.881 + 70 = X

77.881 = X

Hence, 77.88 minutes should be given

14.96

Step-by-step explanation

x/6.5 = 2.3

cross multiply

=> (6.5)(2.3) = 14.96