Question

.average of 17 number is 10.9 the average of first 9 number is 10.5 and the last 9 number is 11.4 what is the middle term?​

Answer 1

Answer:

Hey there! If we know the average of the last 9 numbers, then we can find the middle number (index 9).

Think it this way:

-You know the sum of all the 17 numbers, because you know the average. Let this sum be ‘A’

-You know the sum of first 9 numbers, again because you know the average. Let this sum be ‘B’

If you have sum of the last 9 numbers, let's call it C, then (B + C - A) will give you the middle number since this number has been added twice (once in B, and once in C) and haas been subtracted only once (in A).

Hence, the data is insufficient.