Answer:
The new average is 134/10, or 13.4 years.
Step-by-step explanation:
a + b + c + d + e + f + g + h + i + j
------------------------------------------------ = 13.5 (the original average)
10
15 years is 1.5 year older than the 13.5 average and 11 years is 2.5 younger than that. The net change is 1.5 - 2.5, or -1. The number of players remains the same: 10. We subtract 1 from the sum of the player ages and divide the result by 10:
a + b + c + d + e + f + g + h + i + j - 1
--------------------------------------------------- = 13.4 (the new average)
10
Note that the sum of the original 10 ages is (10)(13.5), or 135, which becomes 134 after the 15-year-old joined the team and the 11 year old quit. The new
average is 134/10, or 13.4 years.
