AlgebraMediumMinimum score for a target average
Algebra practice question
A student's scores on three tests are 78, 92, and 84. What is the least whole-number score the student can get on a fourth test so that the average (arithmetic mean) of the four scores is at least 85?
Answer: 86
(254 + x)/4 ≥ 85 → 254 + x ≥ 340 → x ≥ 86.
Common wrong answers
- If you answered 84
- 84 is the current average of the three (254 ÷ 3 ≈ 84.7) rounded down; the fourth score must pull it up.
- If you answered 85
- 85 gives an average of 84.75, just under 85.
- If you answered 340
- 340 is the total needed, not the fourth score.
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