Multiple choice

The average of 15 results is 35. The average of the first 8 results is 38, and the average of the last 8 results is 34. What is the 8th result?

  1. 53

  2. 48

  3. 51

  4. 45

  5. 57
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The sum of all 15 results is 15 × 35 = 525. The sum of the first 8 results is 8 × 38 = 304. The sum of the last 8 results is 8 × 34 = 272. Since the 8th result is counted in both groups, we have: sum(first 8) + sum(last 8) = total + 8th result. Therefore: 304 + 272 = 525 + 8th result, so 576 = 525 + 8th result, giving 8th result = 51. Option C is correct.

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