Question 984144: How many four-digit numbers, each less than 6000, can be made with the digits 1,3,4,5,7,8,and 9 if a)repetitions are allowed; b)no repetitions are allowed?
Answer by macston(5194)   (Show Source):
You can put this solution on YOUR website! .
With repetition:
Starting from left, for first digit there are 4 choices (less than 6), second digit 7 choices, third digit 7 choices, fourth digit 7 choices:
4 x 7 x 7 x 7=1372
ANSWER: 1372 four digit numbers can be made with repetition.
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Without repetition:
Starting from left, for first digit there are 4 choices (less than 6), second digit 6 choices, third digit 5 choices, fourth digit 4 choices:
4 x 6 x 5 x 4=
ANSWER: 480 four digit numbers can be made without repetition.
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