Mathematics - Permutation & Combination Question with Solution | TestHub

MathematicsPermutation & CombinationFundamental PrincipleEasy2 minQB

MathematicsEasyinteger

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

Answer:

Solution:

For $n = 6$ $3 \times 3 \times 3 \times 3 \times 3 \times 3 = 729 < 900$

For $n = 7$

$3 \times 3 \times 3 \times 3 \times 3 \times 3 \times 3 = 2187 > 900$

For $n = 8$

Number of n-digits formed > 900

Since the least n is required.

$∴ n = 7$ .

Stream:JEESubject:MathematicsTopic:Permutation & CombinationSubtopic:Fundamental Principle

⏱ 2mℹ️ Source: QB

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