Question

You are going to mow your neighbor's lawn for some extra money. Below is a scale drawing of their lawn, where each square represents 5 feet.

1. Prove which type of quadrilateral this lawn is. Insert the image of your work with the final answer in the box below:
It is a rectangle.

2. What is the perimeter of the real lawn (not the scale drawing)?



3. Your neighbor will either pay you $40 as a flat rate, or they will give you $0.03 for each sq. foot (3 cents per square foot). Which would make you the most money? Show all your work on a paper and insert the image with the final answer here

Answer 1

9514 1404 393

Answer:

1. rectangle; parallelogram with 90° angle
2. 150 feet
3. $40 flat rate

Explanation:

1. The slope of AB is ...

mAB = (yB-yA)/(xB-xA) = (4-0)/(6-3) = 4/3

The slope of AD is ...

mAD = (yD-yA)/(xD-xA) = (6-0)/(-5-3) = 6/-8 = -3/4

The product of these slopes is (4/3)(-3/4) = -1, so the segments AB and AD are perpendicular.

The midpoints of AC and BD will be the same if the sum of their coordinates is the same:

A+C = (3, 0) +(-2, 10) = (1, 10)

B+D = (6, 4) +(-5, 6) = (1, 10)

The midpoints of the diagonals of ABCD are the same, so the figure is a parallelogram. One corner angle is 90°, so the parallelogram is a rectangle. The quadrilateral ABCD is a rectangle.

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2. Using the coordinate differences found in part 1, we know the length AB is the hypotenuse of a 3-4-5 triangle, so is 5 grid squares. Similarly, the length of AD is twice that length, so is 10 grid squares. The perimeter in grid squares is ...

P = 2(L+W) = 2(10+5) = 30 . . . . grid squares

Each grid square represents 5 ft, so the perimeter is ...

(30 squares)(5 ft/square) = 150 ft . . . perimeter

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3. The rectangle is 5 × 10 grid squares, or 25 × 50 ft. Then its area is ...

A = LW = (50 ft)(25 ft) = 1250 ft²

At $0.03/ft², the payment for mowing would be ...

($0.03/ft²)(1250 ft²) = $37.50

The $40 flat rate would make you the most money.