Jack has 8 marbles in four colors, with two marbles of each color. He wants to group his marbles into four pairs such that no pair consists of marbles of the same color. What is the number of ways he can do this?
I realised it’s same derangement problem as we solved earlier. Checkout below link.
In above link problem, 4 people order 4 dishes and we have to find number of ways in which no one get correct dish.
It can be parallel to yesterday’s problem, saying 4 color ball ordered 4 balls and no one got correct ball or say not paired.
Hence derangement Solution for 4 would be 9.
Above link can be used for detailed solution.