Let's count them out...
12
20
21
22
23
24
25
26
27
28
29
32
42
52
62
72
82
92
Whew... that makes 18 two-digit numbers that have a "2".
172
04,14,24,34,40,41,42,43,44,45,46,47,48,49,54,64,74,84,94.... OR 19 Digits
A number with more than one digit is typically called a "multi-digit number." This includes any whole number from 10 and above, such as 12, 345, or 6789. These numbers can be classified as two-digit, three-digit, and so on, depending on how many digits they contain.
There is only one such number.
17
18.
172
To find the total number of seven-digit numbers that contain the number seven at least once, we can use the principle of complementary counting. There are a total of 9,999,999 seven-digit numbers in total. To find the number of seven-digit numbers that do not contain the number seven, we can count the number of choices for each digit (excluding seven), which is 9 choices for each digit. Therefore, there are 9^7 seven-digit numbers that do not contain the number seven. Subtracting this from the total number of seven-digit numbers gives us the number of seven-digit numbers that contain the number seven at least once.
04,14,24,34,40,41,42,43,44,45,46,47,48,49,54,64,74,84,94.... OR 19 Digits
A number with more than one digit is typically called a "multi-digit number." This includes any whole number from 10 and above, such as 12, 345, or 6789. These numbers can be classified as two-digit, three-digit, and so on, depending on how many digits they contain.
There is only one such number.
17
There are 195 such numbers.
There are 156 such numbers.
There are 175 such numbers.
-5
-2