Mathematics - Permutation & Combination Question with Solution | TestHub

MathematicsPermutation & CombinationnPr & nCrMedium2 minPYQ_2014

MathematicsMediumsingle choice

The sum of the digits in the unit's place of all the $4$ - digit numbers formed by using the numbers $3, 4, 5$ and $6$ , without repetition is :

Answer:

Solution:

By fixing one digit at unit place we can form toal number without repetition is $3!$

Sum of digits $= 3! . (6 + 5 + 4 + 3)$

$= (6) (18) = 108$ $\{∵ n! = n . (n - 1) . . . 3.2.1\}$

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

⏱ 2mℹ️ Source: PYQ_2014

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