A probability problem by naitik sanghavi

We need to arrange numbers, such that sum of even placed digits - sum of odd placed digits = 11k or 0. So, only combination, 2+3 = 1+5 is possible. Thus we have to find the number of arrangements of 1243 such that even and odd digits don't change their relative positions. Thus, number of numbers divisible by $11 = 2\times 2 \times 2 = \boxed{8}$

not think to be of level four .....only....4213,4312,1243,1342,3124.3421,2134,2431 are the numbers