Question

Find the sum of the 4-digit numbers formed by taking all the digits from 3,4,5,6,7.​

Answer 1

Answer:

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Answer 2

Answer:

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Explanation:

The number of arrangement of 4 different digits taken 4 at a time is given by

4

P

4

=4!=24.

All the four digits will occur equal number of times at each of the positions, namely ones, tens, , hundreds, thousands.

Thus, each digit will occur 24/4=6 times in each of the positions. The sum of digits in one's position will be 6×(1+3+5+7)=96.

Similar is the case in ten's hundred's and thousand's places.

Therefore, the sum will be 96+96×10+96×100+96×1000=106656.