Hi Cynthia,
I would count the number of one digit, two digit and three digit numbers you need.
One digit:
1 to 9 for a total of 9 integers.
Two digits:
10 to 99 which is 99  9 = 90 integers.
Three digits:
100 to 250 which is 250  99 = 151 integers.
This gives a total of 1 9 + 2 90 + 3 151.
Now if you had asked how many distinct digits I would have said 10, they are
0, 1, 2, ···, 9.
Penny
