Nine hundred distinct n-digit

Nine hundred distinct n-digit positive number are to be formed using only the digits 2, 5 & 7. The smallest value of n for which this is possible is

(a) 6 (b) 7 (c) 8 (d) 9

1 Answers

2305

Shaswata Roy ·2013-03-14 04:53:08

\text{No.of ways to fill any of the digit's place = 3}\\\text{(any of the 3 given integers)}

\text{No. of ways to fill in all the n digits =}\\3\times 3\times 3\times \cdots \times 3=3^{n}

3^{7}>900.\\\text{Hence 7 is the smallest integer for which this is possible.}\

\text{Answer-(b)7}

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