Sol. Ans.(b) From 10 to 100
Digit 1 will appear 20 times (10 to 19, 11, 21, 31, 41, 51, 61, 71, 81, 91, 100) = Sum = 20
Digit 2 will appear 19 times (20 to 29, 12, 22, 32, 42, 52, 62, 72, 82, 92) = Sum = 38
Digit 3 will appear 19 times (30 to 39, 13, 23, 33, 43, 53, 63, 73, 83, 93) = Sum = 57
Digit 4 will appear 19 times (40 to 49, 14, 24, 34, 44, 54, 64, 74, 84, 94) = Sum = 76
Digit 5 will appear 19 times (50 to 59, 15, 25, 35, 45, 55, 65, 75, 85, 95) = Sum = 95
Digit 6 will appear 19 times (60 to 69, 16, 26, 36, 46, 56, 66, 76, 86, 96) = Sum = 114
Digit 7 will appear 19 times (70 to 79, 17, 27, 37, 47, 57, 67, 77, 87, 97) = Sum = 133
Digit 8 will appear 19 times (80 to 89, 18, 28, 38, 48, 58, 68, 78, 88, 98) = Sum = 152
Digit 9 will appear 19 times (90 to 99, 19, 29, 39, 49, 59, 69, 79, 89, 99) = Sum = 171
So, desired answer = 38 + 57 + 76 + 95 + 114 + 133 + 152 + 171 + 20 = 19 (2 + 3 + 4 + 5 + 6 + 7 + 8 + 9) + 20 = 19 × 44 + 20 = 836 + 20 = 856.