How many different positive integers exist between 10^3 and 10^4, the sum of whose digits is equal to 2? Choose the correct choice
A) 6 B) 7 C) 5 D) 4 E) 18
So, the numbers should be from 1,000 to 10,000   The following two cases are possible for the sum of the digits to be 2:   1. Two 1's and the rest are 0's:   1,001   1,010   1,100   3 numbers.   2. One 2 and the rest are 0's:   2,000   1 number.   Total = 4 numbers.   Answer:4
<result>D</result>
How many different positive integers exist between 10^3 and 10^4, the sum of whose digits is equal to 2?