Iam creating a new bingo game and i have 40 images available
problem, i need (random of course) 4 by 4 game cards = 16 images in each game card.
how can i calculate how many permutations are there available ?
or better yet,
i want combinations that varied by more than only one image to make it more interesting.
can you me figure it out and or give me ideas to make it more interesting

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z