George's scores on three math tests were 70, 90 and 75. What score does he need on the fourth test to have a final average of 80?
78
79
85
95
To achieve an average score of 80 on four tests, George's total points should be 320 (4 tests x 80 average).
He already has 70 + 90 + 75 = 235 points from the first three tests.
Therefore, he needs to score 85 on the fourth test to achieve a final average of 80.