Final answer:
To calculate the area of one stretcher course of 20 concrete blocks with 1/2 inch thick mortar joints, multiply the total length including joints by the height of a block to get 450 square inches.
Step-by-step explanation:
The question at hand involves calculating the area of a stretcher course of concrete blocks, accounting for the mortar joints between them. To find this area, we will multiply the total length of the course (which includes the blocks and the joints) by the height of a block. Each concrete block is 5 1/8 inches long, which is 5.125 inches when converted to decimal form. The mortar joint adds an additional 1/2 inch to the length of each block in the course. Thus, the length of each block including the mortar joint is 5.125 inches + 0.5 inches = 5.625 inches. The height of each block remains at 4 inches.
For a course of 20 blocks, the total length will be 20 blocks × 5.625 inches = 112.5 inches. The area of one stretcher course can be found by multiplying this total length by the height of the blocks. Therefore, the area is 112.5 inches × 4 inches = 450 square inches.