Question 918490: if repetation is not permited then the six digit us 1,2,3,4,5,7
then how many ways are less than 4000?
Answer by KMST(5328)   (Show Source):
You can put this solution on YOUR website! If repetition is not allowed, using the six digits 1, 2, 3, 4, 5, and 7,
we can make  sequences of 4 digits.
Each of the six digits used has equal chance of being the first digit,
and since of those digits are less than 4,
half of the 4-digit numbers formed will be less than 4000.
That makes  4-digit numbers that are less than 4000.
If the number of digits does not matter, using the six digits 1, 2, 3, 4, 5, and 7,
you can make  1-digit numbers,
 2-digit numbers, and
 3-digit numbers,
for a total of
 numbers that are less than 4000.
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