Question

The average age of the ten people on my basketball team was 13.5, but then a fifteen year old joined our team and an 11 year old quit the team. What is the average age of my team now?

Answer 1

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.