[JEE Advanced 1998] using only digits 2 5 7 nine hundred distinct n digit numbers are to
Using only digits $2,5,7$, nine hundred distinct $n$-digit numbers are to be formed. The smallest $n$ is
(a) $6$
(b) $7$
(c) $8$
(d) $9$
1 Answer
VAVidaara Admin
✓ Vidaara Team
✓ Accepted
· 2d ago
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Correct answer: (b) $7$
$3^n\ge900$: $3^6=729<900\le3^7=2187$, so $n=7$.
JEE Advanced 1998 · Permutations and Combinations — verified solution by the Vidaara Team.
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