I struggle doing a Khan Academy exercise on density and area problems. One of them that I really do not understand is this:
Densities of Metal, a world-famous rock band, put on a show at an arena in Rome last night. The rectangular floor of the arena had an area of 32,000 meters squared and was packed shoulder to shoulder with fans. The band wants to know how many people were at last night's show. They estimate that, on average, each person takes up a circular space with a diameter of 0.8. Since the floor was packed, they assume these circular spaces were tightly packed together in rows and columns. Estimate how many people were at Densities of Metal's rock show based on their assumptions.
When I checked the answer to the problem, it said that I had to find the area of the square surrounding the circle ( this is a visual )https://cdn.kastatic.org/ka-perseus-graphie/71b810792d30f4f02d87f111a0fe89a07f29ffd5.png), and divide the area of the concert with that. What I don't understand is why you need to divide by the area of the square instead of the circle.