How many 3-digit numbers contain exactly one 1 and exactly one 2?
12x
21x
x12
x21
1x2
2x1 6 ways for 1 and 2 to pbe in the number the 'x' can be any of the remaining 8 numbers (3 4 5 6 7 8 9 0)
6 * 8 = 48
*** EDIT ****
SInce you probably do not want leading zeroes in your 3 digit number
x 21 and x 12 would not be on the list
48 -2 = 46 numbers as Guest below computed
102 120 123 124 125 126 127 128 129 132 142 152 162 172 182 192 201 210 213 214 215 216 217 218 219 231 241 251 261 271 281 291 312 321 412 421 512 521 612 621 712 721 812 821 912 921 >>Total permutations = 46 such numbers.
