11 consecutive integers

[sanjana]

if 11 consecutive integers are listed from least to most,what is the mean of the 11 digits?

a)Average of the 1st 9 is 7
b)Average of the last 9 is 9

[spoiler]OA : D[/spoiler]

[JeffB]

if 11 consecutive integers are listed from least to most,what is the mean of the 11 digits?

a)Average of the 1st 9 is 7
b)Average of the last 9 is 9

[spoiler]OA : D[/spoiler]

For A:
Since we have consecutive integers x + (x+1) etc.

x + (x+1)....(x+8)= 7

You can solve for x (which is your first integer)...Suff

For B:
Same as a

start with (x+2)....(x+10) = 9

Solve for x again..Suff