Pie Chart: Pie charts are useful for showing proportions or percentages of a whole. They divide a circle into slices to represent different categories. In the context of comparing the number of sales across 50 US states, using a pie chart could make it difficult to accurately compare absolute numbers because the slices (representing each state) do not easily convey precise quantities. It's challenging to discern small differences in magnitude or exact values between states in a pie chart, especially when dealing with a large number of categories (50 states).