Question 617261: How many 3-digit numbers with no repeated digits using 4,5,6,7,8 can be less than 520?
Answer by KMST(5328)   (Show Source):
You can put this solution on YOUR website! Because the 3-digit number must be less than 520, the digit in the hundreds place can only be 4.
Then you can pick any of the remaining 4 numbers for the tens place, leaving the other 3 numbers as possible choices for the units digit.
All in all, you get 4 choices for the tens place, and for each of those choices, 3 choices for the units place.
The total number of possible 3-digit numbers is 4 times 3,  .
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