Hi All,
We're asked how much greater the average (arithmetic mean) of the integers from 200 to 400, inclusive, is than the average of the integers from 50 to 100, inclusive.
When dealing with a series of consecutive integers, if we have an ODD number of integers, then the average is the 'middle' value. There are exactly 201 integers from 200 to 400, inclusive - so the average is the number in the 'middle': 300. There are exactly 51 integers from 50 to 100, inclusive - so the average is the number in the 'middle': 75.
The difference in those averages is 300 - 75 = 225.
Final Answer: D
GMAT assassins aren't born, they're made,
Rich