• 10/1

  • 17/1

  • 20

  • 21


Clearly, from 1 to 100, there are ten numbers with 3 as the units digit- 3, 13, 23, 33, 43, 53, 63, 73, 83, 93; and ten numbers with 3 as the tens digit - 30, 31, 32, 33, 34, 35, 36, 37, 38, 39. So, required number = 10 + 10 = 20.