Question : The average of 15 results is 21. The average of the first 7 of those is 21 and the average of the last 7 is 20. What is the 8th result?
Option 1: 25
Option 2: 31
Option 3: 28
Option 4: 22
Correct Answer: 28
Solution : The average of 15 results is 21, which means the sum of all 15 results is 15 × 21 = 315. The average of the first 7 results is 21, which means the sum of the first 7 results is 7 × 21 = 147. The average of the last 7 results is 20, which means the sum of the last 7 results is 7 × 20 = 140. So, the 8th result = Sum of all 15 results – Sum of first 7 results – Sum of last 7 results = 315 – 147 – 140 = 28 Hence, the correct answer is 28.
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Question : The average of 25 results is 20. The average of the first 12 results is 15 and that of the last 12 results is 18. Then the 13th result is:
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