Between 200 and 400 there are 18 whole numbers that contain the digit 7 once and only once: 207, 217, 227, 237, 247, 257, 267, 287, 297, 307, 317, 327, 337, 347, 357, 367, 387, and 397.
9876543120
If the same digit can be used more than once: 6 x 6 x 6 = 216 of them. If each digit can be used only once: 6 x 5 x 4 = 120 of them.
135 + 246 = 381 You can swap the digits in the hundreds' place between the two numbers, the tens' place and the units' place, for example, 145 + 236 (tens')
333
19.
19 or 20 ( if you count 66 as double)
Infinitely many.
19 of them
Eighteen of them from 9 to 98
252
19 do.
990
Between 200 and 400 there are 18 whole numbers that contain the digit 7 once and only once: 207, 217, 227, 237, 247, 257, 267, 287, 297, 307, 317, 327, 337, 347, 357, 367, 387, and 397.
Twenty of them from 9 to 99
theres only 1 number which is 123456, the least digit is 1 and the greatest is 6
It is .56789