1 one between 1 and 9, and similarly for 20-29, 30-39, 40-49, 50-59, ..., 90-99 (9 in all);
11 1s between 10 and 19;
20 1s between 1 and 99 and between 200 and 300.
100 1s between 100 and 199 in the hundreds position plus 20 in the tens and ones positions=120 1s.
Total of 1s is 20 (1-99) + 120 (100-199) + 20 (200-300) = 160 1s.
The table shows only numbers containing 1s. The row and column totals of ones are shown in bold print.
