The volume of the box can be calculated by multiplying all of the dimensions together since this models a rectangular prism.
We convert the width and height into feet. The length of the box is 6 feet, the width of the box is 3 in * 1 ft/12 in = 0.25 feet, and the height is 9 in * 1 ft/12 in = 0.75 ft.
volume box = 6 * 0.25 * 0.75 = 1.125 ft^3
We divide the volume of the box by the volume of fertilizer in each bag.
number of bags = 1.125 ft^3/0.225 ft^3
= 5 bags
The answer to this question is it will take 5 bags of fertilizer.