First of all, we need to compute the volume of a 100 dollars bills. A quick search on Google tells us that
"The $100 bill is the same size as all other US currency. All US paper currency is 2.61 inches wide and 6.14 inches long, 0.0043 inches thick and weigh 1 gram"
So, since the bill is a rectangular prism, its volume is given by the product of its three dimensions. So, you have
cubed inches.
Now, the volume of the bill is expressed in cubic inches, while the volume of the container is expressed in cubic foot. We need a conversion, and since there are 12 inches in 1 foot, there are cubic inches in a cubic foot.
So, we have a volume of 1728 cubic inches, and we want to know how many 0.06890922-cubed-inched bills we can fit in it.
Since one bill has a volume of 0.06890922 cubic inches, bills have a volume of . We want to choose in such a way that it fill a 1728 cubic inches volume, so the equation is
So, about 25 thousands bills would fit in a cubic foot.