Multiple choice

A student's average (arithmetic mean) test score on $4$ tests is $78$.What must be the student's score on a $5^{th}$ test for the student's average score on the $5$ tests to be $80 $?

  1. $80$
  2. $82$
  3. $84$
  4. $86$
  5. $88$
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E Correct answer
Explanation

The sum of the first 4 scores is 4 * 78 = 312. The sum of the 5 scores must be 5 * 80 = 400. The 5th score is 400 - 312 = 88.

AI explanation

The total score needed for 5 tests to have an average of 80 is 5 multiplied by 80, which equals 400. The current total score for the 4 tests is 4 multiplied by 78, which equals 312. The score required on the fifth test is the difference between the target total and the current total, so 400 minus 312 equals 88.

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