Question

Blair's average (arithmetic mean) on two physics tests is 7. What should Blair's score be on the next test to have an overall average of 8 for all the tests?

A. 7
B. 8
C. 9
D. 10

Answer 1

To achieve an average of 8 after three tests, starting with an average of 7 after two tests, Blair needs to score 10 on the next test. The correct answer is D. 10.

Step-by-step explanation:

To calculate the score Blair needs on the next physics test to have an overall average of 8, we first need to determine the total points Blair currently has from the two tests taken. Since the arithmetic mean of these two tests is 7, we multiply this by 2 (the number of tests) to get the total points, which is 14 (7 × 2 = 14). To achieve an overall average of 8 after three tests, Blair needs the sum of all three test scores to equal 24 (8 × 3 = 24).

Next, we subtract the total points Blair already has from what is needed for an average of 8. This calculation gives us 24 - 14 = 10. Therefore, Blair must score 10 on the next physics test to reach an overall average of 8.

So the correct answer is D. 10.