SOLUTION: How many three-digit counting numbers that are less than 300 are there such that all the digits are odd?

Question 67227This question is from textbook Advanced mathematics
: How many three-digit counting numbers that are less than 300 are there such that all the digits are odd? This question is from textbook Advanced mathematics

Answer by 303795(602) (Show Source): You can put this solution on YOUR website!
The only numbers below 300 must be in the one hundreds so the first digit must be 1.
The second digit can be 1, 3, 5, 7 or 9.
Five numbers with a second digit of 1 have an odd third digit.
Five numbers with a second digit of 3 have an odd third digit.
Five numbers with a second digit of 5 have an odd third digit.
Five numbers with a second digit of 7 have an odd third digit.
Five numbers with a second digit of 9 have an odd third digit.
So the total is 25 numbers.
111, 113, 115, 117, 119, 131, 133, 135, 137, 139, 151, 153, 155, 157, 159, 171, 173, 175, 177, 179, 191, 193, 195, 197, 199

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