Question

Difficulty: MediumPerimeter and Area of 2D Figures

A rectangular parking lot has a perimeter of 200200 yards. The length of the parking lot is 4040 yards greater than its width. What is the area of the parking lot, in square yards?

Answer: 2100 sq yd

Answer

2100
The correct answer is derived by first finding the individual dimensions using the perimeter formula and the given relationship (l=w+40l = w + 40), which gives a width of 30 yards and a length of 70 yards. Multiplying these dimensions yields an area of 2100 square yards.

Step-by-Step Solution

1
Write the perimeter formula for a rectangle.
P=2l+2wP = 2l + 2w
The perimeter is the total distance around the rectangle.
2
Translate the given information into equations.
2l+2w=2002l + 2w = 200 and l=w+40l = w + 40
The problem states the perimeter is 200 yards and the length is 40 yards greater than the width.
3
Substitute the expression for length into the perimeter equation and solve for width.
2(w+40)+2w=200⇒2w+80+2w=200⇒4w=120⇒w=302(w + 40) + 2w = 200 \Rightarrow 2w + 80 + 2w = 200 \Rightarrow 4w = 120 \Rightarrow w = 30
Substitution allows us to create an equation with only one variable.
4
Calculate the length.
l=30+40=70l = 30 + 40 = 70
Now that we know the width is 30 yards, we can add 40 to find the length.
5
Calculate the area of the rectangle.
Area=l×w=70×30=2100Area = l \times w = 70 \times 30 = 2100
The area of a rectangle is found by multiplying its length by its width.

Key Concept

Using algebraic equations to find the dimensions of a rectangle from its perimeter, and then calculating its area.
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