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?

• A. 25
• B. 31
• C. 28
• D. 22

Answer 1

Answer:

C. 28

Average = Sum of all values / Number of all values Sum of total 15 results = 15 × 21 = 315 Sum of first 7 results = 21 × 7 = 147 Sum of last 7 results = 20 × 7 = 140 Total sum of 14 results = 147 + 140 = 287 Value of 8th term = 315 – 287 = 28