1 answer
(click or scroll down)
I will assume that you know how to find the area of a circle. In this case, that will be π ft^2
I must also assume you haven't studied packing density of circles, so we'll say the centers of the circles lie on a square grid. That said, since each circle has diameter 2, the piece of tin is 5x2 circles in size.
So, the leftover area is 10*4-10Ï€ = 40-31.4 = 8.6 or 9 ft^2