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?
Answer & explanation
Correct answer: option 3
Sum of 15 results = 15 x 21 = 315
Sum of 1st 7 results = 7 x 21 = 147
Sum of last 7 results = 7 x 20 = 140
8th result = 315 - 147 - 140 = 28