CIE
9709_s10_qp_62
Q 7 (ii).
I just want to know any short method, i have got the answer but with a way too long method.
as the markscheme suggests, its simple.
The no. of ways the pink card is not next to the green card = Total no. of ways - (the no. of ways the green card and the pink are together)
The no. of ways the pink and green are together...
There is a very neat trick to find this, it's in there in the CIE S1 book
U consider the 2 cards as a unit, and permute them with the other 7
Like this [pink, green] + 7 others... = total 8 (regarding the pink, green as one unit)
The permutation = 2*8!
Subtract this from 9! and u have ur answer
9!-(2*8!)