+80 Hi,
How many ways are there to shade a total of 8 unit squares in a 4 times 4 grid such that there are exactly 2 shaded squares in each row and each column?
I thought it was simple, until i started doing it. could somebody provide me a solution?
Also, Andrew, Bob, and Chalie decide to split 6 pennies, 8 dimes, and 9 quarters (not neccessarily equallly.) How many ways are there to distribute the coins so that each person receives at least as many quarters as dimes and at laest as many dimes as pennies?
Two grandparents, two parents, a pair of twin girls and a boy decide to take a family photo. In how many ways can they arrange themselves in a line if the boy insists on standing in between either both the twin girls, both the parents, or both the grandparents?
