n-digit numbers are formed using only three digits 2, 5 and 7. The smallest value of n for which 900 such distinct numbers can be formed, is :
As we learned
Number of Permutations with repetition -
The number of ways of filling r places where each place can be filled by any one of n objects.
It is
- wherein
Where
Option 1)
Option 2)
Option 3)
Option 4)
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