Analysis: The largest three digits are 999, and the smallest two digits are 10. Just calculate the sum and difference of 999 and 10.

Answer:

The largest three digits are 999, and the smallest two digits are10;

999- 10=989;

999+ 10= 1009;

So the difference between the largest three digits and the smallest two digits is 989, and the sum is 1009.

Extended data

Addition and subtraction of numbers within 10 thousand.

Steps of vertical addition within ten thousand columns:

1, column vertical;

2. The same numbers must be aligned;

3. When the number on a digit adds up to ten, you need to advance to the previous digit1; If the last one is also full of ten, go to the last one and enter1;

4. write the answer.

Operation steps of vertical subtraction within ten thousand columns:

1, column vertical;

2. The same numbers must be aligned;

3. When subtracting, if the number on which bit is insufficient, borrow1from the previous bit; If the previous digit is 0, 1 is borrowed from the previous digit.

4. write the answer.