Final answer:
By setting up a system of equations with the given perimeter formula and dimensions relationship, we determine the dimensions of the rectangular base to be 310 ft by 125 feet.
Step-by-step explanation:
To determine the dimensions of a rectangular base where the length is 65 ft less than three times the width, and the perimeter is 870 ft, we can set up a system of equations. Let w represent the width of the rectangle, and l represent the length of the rectangle. From the problem, we have:
l = 3w - 65
Now, using the formula for perimeter of a rectangle (P = 2l + 2w), we can write:
870 = 2(3w - 65) + 2w
Solving for w, we find:
870 = 6w - 130 + 2w
870 + 130 = 8w
w = 1000 / 8
w = 125 feet
Substitute w back into the equation for l:
l = 3(125) - 65
l = 375 - 65
l = 310 feet
Therefore, the dimensions of the building are 310 ft by 125 feet.