Depends on how deep he wants it to go. Let's say 3 inches. That would be about 5 yards of mulch, or 135 cubic feel, or 45 bags.
It would be much, much easier and cheaper to have your mulch delivered by a local landscape supplier. They sell by the yard (much more cheaply than buying bags) and usually deliver for free for an order as big as 5 yards.
Buying mulch in bags is a fool's bet, unless you only need a very small amount.
(525 x depth in feet) / 3 = number of bags
length x width x thickness divided by 27 = cubic yards
My dad as 525 square feet of surface that he needs to cover with mulch, and the bags cover 3 cubic feet, how many bags of mulch does he meed to buy?
