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### BDMO National Junior 2018/7

Posted: **Tue Jan 08, 2019 1:53 pm**

by **nahin munkar**

All possible $4$ digit numbers are created using $5,6,7,8$ and then sorted from smallest to largest. In the same manner, all possible $4$ digit numbers are created using $3,4,5,6$ and then sorted from smallest to largest. Then first number of the second type is subtract from first number of the first type, second number of the second type is subtract from second number of the first type and so on. What will be the summation of these difference (subtraction results) ?

### BdMO National Junior problem 7

Posted: **Thu Jan 10, 2019 1:49 am**

by **samiul_samin**

You can get the problem here

Short solution

### Re: BDMO National Junior 2018/7

Posted: **Wed Jan 16, 2019 11:22 pm**

by **prottoy das**

Probably it will be $4^4$ permutations. Because here, it is not said that a digit will be written one time in a number

### Re: BDMO National Junior 2018/7

Posted: **Thu Jan 17, 2019 1:48 pm**

by **samiul_samin**

prottoy das wrote: ↑Wed Jan 16, 2019 11:22 pm

Probably it will be $4^4$ permutations. Because here, it is not said that a digit will be written one time in a number

I really missed that