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Mathematics - Permutation & Combination Question with Solution | TestHub

MathematicsPermutation & CombinationnPr & nCrMedium2 minPYQ_2018

MathematicsMediumsingle choice

$n$ -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 :

Options:

Answer:

Solution:

$n$ - digit number are formed using only three digits $2, 5$ and $7$ with repetition $= 3^{n}$ .

Since, $3^{6} < 900$ and $3^{7} > 900$

So, $n = 7$ .

Stream:JEESubject:MathematicsTopic:Permutation & CombinationSubtopic:nPr & nCr

⏱ 2mℹ️ Source: PYQ_2018

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