Question

Markus scored 85, 92, 82, and 94 on the first four tests of the semester. his teacher has not yet told him his score on his fifth test, but did tell him that his score on the fifth test is five points lower than the average (arithmetic mean) of all five tests. which equation could markus use to determine the score of the fifth test, x

Answer 1

The average of the set of numbers is the quotient when the sum of the numbers is divided by the number of items. Given that Markus' fifth score x, the average is x+5. The equation for solving the fifth score and the arithmetic mean is, 
                         (85 + 92 + 82 + 94 + x) / 5 = x + 5
Further simplifying gives, 
                           (353 + x) / 5 = x + 5
Calculating for the value of x gives x = 82.