The average of 9 results is 59. The average of the first 5 results is 64 and the average of the last 5 results is 62. What is the 5th result?

💡 Solution & Explanation

The first 5 and the last 5 results together make 10 results, but there are only 9: the 5th result is counted in both groups. Sum of the first 5 = 5 × 64 = 320; sum of the last 5 = 5 × 62 = 310; sum of all 9 = 9 × 59 = 531. So the 5th result = 320 + 310 − 531 = 99.