Question

Shelby will take a total of 6 tests. On the first 5 tests, her scores were: 80, 85, 73, 78, 90. If she wants a mean grade of 80, what does Shelby have to score on her 6th test?

84
80
90
74

Answer 1

74

Explanation:

The mean of any set of numbers is simply the sum of the numbers divided by however many numbers you have. Because of this you can write the following equation

Mean = (sum of numbers)/(number of numbers)

Let's say that the missing test score is called x:

Mean = 80 = (80 + 85 + 73 + 78 + 90 + x)/6

80(6) = 80 + 85 + 73 + 78 + 90 + x

480 = 80 + 85 + 73 + 78 + 90 + x

x = 480 - 80 - 85 - 73 - 78 - 90

x = 74