4 digit no.

\hspace{-16}$Find Sum of $\bf{4}$ digit no. that can be formed with the digit $\bf{1,2,3,4,5....,9}$\\\\ Repetition not allowed

1 Answers

262

Aditya Bhutra ·2012-05-03 23:17:15

total no. of such numbers = ⁹P₄

thus for units digit , each number from 1,...9 appears ⁹P₄ /9 times

sum of units place = ⁹P₄ /9 * (1+2+3 + ... +9) = 630

similarly for tens , hundreds and thousands digits .

thus total sum of numbers = 630*( 10⁰ + 10¹ + 10² +10³) = 699930

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