180
91.
16
100C3= 100x99x98/3!= 161700 The notation is 100 choose 3
Write out the numbers 1 to 100. Count the number of times 1 appears.
-99
525
I believe here are 51 such numbers.
180
900, all numbers from 100 to 999 inclusive.
90. all the numbers from 10 through 99
-99
252 of them.
176
91.
16
10