if you spread a billion 1-dollar bills on the ground, how many square miles would they cover

find the area of a 1 dollar bill, multiply it by a billion, voila! problem solved!

Area of one dollar bill = 100.75 cm^2

Area of 1 billion of them = 100750000000 cm^2 = 1.0075 x 10^11 (1)

Number of sq cm to 1 sq mi ≈ 2.59 x 10^10 cm^2 (2)

So.....the answer is given by (1) / (2) ≈ 3.9 sq mi