Multiple choice

Andrew has taken $5$ of the $8$ equally weighted tests in his U.S. Maths class this semester, and he has an average score of exactly $78.0$ points. How many points does he need to earn on the $6^{th}$ test to bring his average score up to exactly $80.0$ points?

  1. $90$
  2. $88$
  3. $82$
  4. $80$

  5. 79
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A Correct answer
Explanation

Total points needed for 8 tests = 8 * 80 = 640. Current points = 5 * 78 = 390. Points needed for remaining 3 tests = 640 - 390 = 250. This question implies the 6th test is the only one left to reach the average, but it asks for the 6th test specifically. If he needs to reach 80 average after 6 tests, he needs 6 * 80 = 480 total. 480 - 390 = 90.

AI explanation

The total points needed for 6 tests to achieve an average of 80 is 6 multiplied by 80, which equals 480. Andrew's current total points from the 5 tests he has taken is 5 multiplied by 78, equaling 390. The points he must earn on the sixth test are the difference between the target total and his current total, so 480 minus 390 equals 90.

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