We call a natural number "odd looking" if all its digits are odd.How many 4-digit odd looking numbers are there?

Each of the 4 places can be filled with any of the 5 odd digits

number of "odd-looking" number
= 5*5*5*5
= 625 , assuming that digits my be repeated

To find the number of 4-digit odd looking numbers, we need to determine the range of possible values for each digit.

Since all the digits must be odd, the possible values for each digit are 1, 3, 5, 7, and 9.

For the thousands digit (the leftmost digit), it cannot be 0, so we have 5 choices.

Similarly, for the hundreds digit, tens digit, and units digit, each has 5 choices.

Therefore, the total number of 4-digit odd looking numbers is given by:

5 * 5 * 5 * 5 = 625

So, there are 625 4-digit odd looking numbers.

To find the number of 4-digit odd looking numbers, we need to consider the restrictions on the digits:

1. The first digit cannot be zero. It can be any odd digit from 1 to 9.
2. The remaining three digits can also be any odd digit from 1 to 9.

We can solve this problem using multiplication principle:

Step 1: Count the number of choices for each digit position:

- For the first digit (thousands place), we have 5 choices (1, 3, 5, 7, or 9).
- For the second (hundreds), third (tens), and fourth (ones) digit, we also have 5 choices for each.

Step 2: Multiply the number of choices together:

5 choices for the first digit * 5 choices for the second digit * 5 choices for the third digit * 5 choices for the fourth digit = 5^4 = 625

Therefore, there are 625 odd looking 4-digit numbers.