Question 799232: how many numbers consisting of the digits from 3,5,7,9 can be made if (a)each digit is to be used only once (b) repetition is allowed.
Found 2 solutions by thejackal, solver91311:
Answer by thejackal(72)   (Show Source):
You can put this solution on YOUR website! n = 4, there 4 types of values you can choose from i.e. 3,5,7 or 9
r = 4, of these 4types you must produce a combination that has 4 digits
thus the total number of possible combinations is found using the formula
(n+r-1)!/r!(n-1)!
if and only if repetitions are allowed.
Combinations with repetition (n=4, r=4)
35 entries.
{3,3,3,3} {3,3,3,5} {3,3,3,7} {3,3,3,9} {3,3,5,5} {3,3,5,7} {3,3,5,9} {3,3,7,7} {3,3,7,9} {3,3,9,9} {3,5,5,5} {3,5,5,7} {3,5,5,9} {3,5,7,7} {3,5,7,9} {3,5,9,9} {3,7,7,7} {3,7,7,9} {3,7,9,9} {3,9,9,9} {5,5,5,5} {5,5,5,7} {5,5,5,9} {5,5,7,7} {5,5,7,9} {5,5,9,9} {5,7,7,7} {5,7,7,9} {5,7,9,9} {5,9,9,9} {7,7,7,7} {7,7,7,9} {7,7,9,9} {7,9,9,9} {9,9,9,9}
Answer by solver91311(24713)  (Show Source):
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