If the two solids have the same height and same cross-sectional area at every level, this means that the radius of the oblique cylinder is the same as the radius of the right cylinder.
Since the radius of the right cylinder is 16/2=8, this means that the radius of the oblique cylinder must also be 8.
We all know that area= LxW The width that is being shown is 8ft. The length is 20ft. Therefore, you multiply 8 x 20 which gives you 160ft squared. Hope this this helps :)
