Basic concepts of permutations and combination

You can solve this way

Soumya A

CA Inter

★ 20K+

08-Sep-21 15:03

I can't understand

Thread Starter

Sejal Shivani

CA Foundation

★ 5K+

08-Sep-21 16:15

I hope now you can understand

Soumya A

CA Inter

★ 20K+

08-Sep-21 18:05

Ok thanks

Thread Starter

Sejal Shivani

CA Foundation

★ 5K+

08-Sep-21 18:08

:)

Soumya A

CA Inter

★ 20K+

08-Sep-21 18:09

Well explained. Adding explanation for more clarity - So, total such 4 digit numbers will be 24. Now, each digit i.e. 2, 4, 6 or 8 will be at unit, tens, hundred and thousand place 6 times (3!) each. Example 2468, 2486, 2684, 2648, 2846, 2864 - this is nothing but, permutation of other 3 digits - 3! with 2 as fixed. Number, 2468 - can also be written as 8 X 1 + 6 X 10 + 4 X 100 + 2 X 1000. Now since we know each digit will be at each place 6 times, sum of all can be Numbers ( 1 + 10 + 100 + 1000) X 6. So, this is what she has done in her solution. There is also a direct formula you can apply in such cases as attached. Best wishes!

Sahibdeep Singh

CA Inter

★ 14K+

08-Sep-21 18:11

Ok thank you sir

Thread Starter

Sejal Shivani

CA Foundation

★ 5K+

08-Sep-21 18:16