Question

A gardener is planning to fill her garden with mulch. She plots it on a grid to plan how much she will need. The garden is in the shape of a rectangle with vertices at (3, 9) (5, 9) (3, 3) (5, 3). One bag of mulch covers 5ft2 and costs $5.00. How much will it cost her to cover her garden?

Answer 1

First we need to know the total area. Since this is a rectangle we need two adjacent sides and we can find these from vertex pairing: 

Matching y: (3,9) --> (5,9) = 2 ft
Matching x: (3,9) --> (3,3) = 6 ft

Area = l*w = 2*6 = 12 square ft

# of bags = 12sqft/(5sqft/bag) = 2.4 bags. 

Cost = $5.00 * 2.4 = $12   (notice that it cost $1 to cover 1sqft so we could have skipped a step here.)

NOTE: In the real world she probably can't buy just 0.4 of a bag and would actually have to buy three full bags for $15.