Posted by Anonymous on Monday, March 11, 2013 at 2:30am.
first digit: 9 choices (1-9)
then, 2nd digit: 9 choices (now 0 is allowed)
then, 3rd digit: 8 choices
so, 9*9*8
It has to be odd, so the 3rd digit has to be 1, 3, 5, 7, or 9. So there are only 5 options. Moreover, you do not consider the cases in which the digits do not repeat.
you got me on the odd value, but I do account for the non-repeatability of digits.
If they can be repeated, then there would be 9*10*10 possibilities for 3 digits.
My counting forces the preceding choices not to be used again.
Since the number must be odd, things get a bit more complicated, because we don't know whether the previous choices were odd or even.
You seem to have a handle on the problem. What is your reasoning?
Related Questions
math..probabilities - After three tosses of a fair die, which is more likely to ...
DISCRETE MATH - HOW MANY POSITIVE INTEGERS LESS THAN 1000 A.are divisible by ...
Math - There are three distinct ways to add four positive odd numbers to obtain ...
Math - There are three distinct ways to add four positive odd numbers to obtain ...
4th grade math - Find the mystery number. It is a 4 digit odd number. All the ...
math - *The number has 8 digits, none of the digits are the same. *It is evenly ...
math - find the mystery number, it is a 4 digit odd number, all the digits are ...
math - What mystery number has 8 digits; none of the digits are the same. It is ...
math - Get the number right. *None of the digits repeat. *It is between 20,000 ...
math - The number has 8 digits none of the digits are the same 2. It is enemy ...
For Further Reading
