The difference between the smallest number of 7 digits and the largest number of 4 digits is ____.

Solution:

The difference between the smallest number of 7 digits and the largest number of 4 digits is 990001.
We need to subtract the largest number of 4 digits from the smallest number of 7 digits.
The smallest number of 7 digits is 1000000.
The largest number of 4 digits is 9999.
Difference = smallest number of 7 digits - largest number of 4 digits.
Difference = 1000000-9999
The number 9999 can be written as the difference between 10000 and 1.
9999 = 10000 -1
Difference = 1000000 - (10000 - 1).
According to arithmetic rules,

(−) × (+) = (−) and (−) × (−) = (+) .

Difference = (1000000 + 1) - 10000
Difference = 1000001 - 10000 = 990001
Therefore, the difference between the smallest number of 7 digits and the largest number of 4 digits is 990001.
Therefore, the answer is 990001.