6 × 4 grid is divided into unit squares, Find the number of squares, of any size, in the grid.

George has a pair of unusually labelled dice. One die is labeled with the numbers 1, 2, 2, 3, 3, and 4. The other die is labelled with the numbers 1, 3, 4, 5, 6, and 8. He rolls both dice at random. What is the probability that the sum of the numbers is 6?

How many ways can you divide nine children into a team of 4, a team of 3, and a team of 2?

Ana writes down all the numbers 1, 2, . . . , n, for some positive integer n. In doing so, she writes a total of 600 digits. Find the positive integer n.