Question
An n-digit number is a positive number with exactly n digits. Nine hundred distinct n-digit numbers are to be formed using only the three digits 2, 5 and 7. The smallest value of n for which this is possible is
Answer: Option B
:
B
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B
Since at any place, any of the digits 2, 5 and 7 can be used, total number of such positive n-digit numbers are 3n. Since we have to form 900 distinct numbers, hence 3n≤900⇒n = 7
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