Problem Solving (PS) | Re: How many positive integers less than 1000 are there in which the sum o

Straightforward if you divide possible numbers up into different 'buckets':

1. Single digit numbers
2. Double digit numbers
3. Triple digit numbers

For #1: we only have 1 option, 4

For #2: we have 13/31/22/40 = 4 options

For #3: we have 112 (and its combinations = 3!/2! = 3) + combinations of 202 (=2) + combinations of 103 (= 2*2*1 = 4) + 400 = 3+2+4+1 = 10

Thus,
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