High School Math : Rectangles

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : Rectangles

The rectangular bathroom floor in Michael’s house is ten feet by twelve feet. He wants to purchase square tiles that are four inches long and four inches wide to cover the bathroom floor. If each square tile costs $2.50, how much money will Michael need to spend in order to purchase enough tiles to cover his entire bathroom floor?

Possible Answers:

$4800

$1080

$5400

$1920

$2700

Correct answer:

$2700

Explanation:

The dimensions for the bathroom are given in feet, but the dimensions of the tiles are given in inches; therefore, we need to convert the dimensions of the bathroom from feet to inches, because we can’t compare measurements easily unless we are using the same type of units.

Because there are twelve inches in a foot, we need to multiply the number of feet by twelve to convert from feet to inches.

10 feet = 10 x 12 inches = 120 inches

12 feet = 12 x 12 inches = 144 inches

This means that the bathroom floor is 120 inches by 144 inches. The area of Michael’s bathroom is therefore 120 x 144 in2 = 17280 in2.

Now, we need to find the area of the tiles in square inches and calculate how many tiles it would take to cover 17280 in2.

Each tile is 4 in by 4 in, so the area of each tile is 4 x 4 in2, or 16 in2.

If there are 17280 in2 to be covered, and each tile is 16 in2, then the number of tiles we need is 17280 ÷ 16, which is 1080 tiles.

The question ultimately asks us for the cost of all these tiles; therefore, we need to multiply 1080 by 2.50, which is the price of each tile.

The total cost = 1080 x 2.50 dollars = 2700 dollars.

The answer is $2700.

Example Question #321 : Plane Geometry

Ron has a fixed length of wire that he uses to make a lot. On Monday, he uses the wire to make a rectangular lot. On Tuesday, he uses the same length of wire to form a square-shaped lot. Ron notices that the square lot has slightly more area, and he determines that the difference between the areas of the two lots is sixteen square units. What is the positive difference, in units, between the length and the width of the lot on Monday?

Possible Answers:

12

4

10

8

6

Correct answer:

8

Explanation:

Let’s say that the rectangular lot on Monday has a length of l and a width of w. The area of a rectangular is the product of the length and the width, so we can write the area of the lot on Monday as lw.

Next, we need to find an expression for the area of the lot on Tuesday. We are told that the lot is in the shape of a square and that it uses the same length of wire. If the length of the wire used is the same on both days, then the perimeter will have to remain the same. In other words, the perimeter of the square will equal the perimeter of the rectangle. The perimeter of a rectangle is given by 2l + 2w.

We also know that if s is the length of a side of a square, then the perimeter is 4s, because each side of the square is congruent. Let’s write an equation that sets the perimeter of the rectangle and the square equal.

2l + 2w = 4s

If we divide both sides by 4 and then simplify the expression, then we can write the length of the square as follows:

Recsquare1

Recsquare2

Example Question #11 : Rectangles

A rectangle has a width of 2x.  If the length is five more than 150% of the width, what is the area of the rectangle?

Possible Answers:

5x + 10

5x + 5

6x2 + 10x

10(x + 1)

6x2 + 5

Correct answer:

6x2 + 10x

Explanation:

Given that w = 2x and l = 1.5w + 5, a substitution will show that l = 1.5(2x) + 5 = 3x + 5.  

A = lw = (3x + 5)(2x) = 6x2 + 10x

Example Question #1 : How To Find The Area Of A Rectangle

Para-rec1

Rectangle ABCD is shown in the figure above. Points A and B lie on the graph of y = 64 – x2 , and points C and D lie on the graph of y = x2 – 36. Segments AD and BC are both parallel to the y-axis. The x-coordinates of points A and B are equal to –k and k, respectively. If the value of k changes from 2 to 4, by how much will the area of rectangle ABCD increase?

Possible Answers:

88

272

176

544

352

Correct answer:

176

Explanation:

Para-rec2

Para-rec3

Example Question #322 : Plane Geometry

George wants to paint the walls in his room blue.  The ceilings are 10 ft tall and a carpet 12 ft by 15 ft covers the floor.  One gallon of paint covers 400 ft^{2} and costs $40.  One quart of paint covers 100 ft^{2} and costs $15.  How much money will he spend on the blue paint?

Possible Answers:

Correct answer:

Explanation:

The area of the walls is given by

One gallon of paint covers 400 ft^{2} and the remaining 140 ft^{2} would be covered by two quarts.

So one gallon and two quarts of paint would cost

Example Question #2 : Rectangles

Daisy gets new carpet for her rectangluar room.  Her floor is 21\ ft \times 24\ ft.  The carpet sells for $5 per square yard.  How much did she spend on her carpet?

Possible Answers:

\$350

\$280

\$310

\$225

\$120

Correct answer:

\$280

Explanation:

Since 3\ ft=1\ yd the room measurements are 7 yards by 8 yards.  The area of the floor is thus 56 square yards.  It would cost 5\cdot 56=\$280.

Example Question #212 : Geometry

The length of a rectangular rug is five more than twice its width.  The perimeter of the rug is 40 ft.  What is the area of the rug?

Possible Answers:

50\ ft^{2}

150\ ft^{2}

75\ ft^{2}

125\ ft^{2}

100\ ft^{2}

Correct answer:

75\ ft^{2}

Explanation:

For a rectangle, P=2w+2l and A=lw where w is the width and l is the length.

Let x=width and 2x+5=length.

So the equation to solve becomes 40=2x+2(2x+5) or 40=6x+10.

Thus x=5\ ft and 2x+5=15\ ft, so the area is 75\ ft^{2}.

Example Question #3 : How To Find The Area Of A Rectangle

The length of a rectangle is 5 times its width. Its width is 3 inches long. What is the area of the rectangle in square inches?

Possible Answers:
36
75
15
45
Correct answer: 45
Explanation:

The length is 5 x 3 = 15 inches. Multiplied by the width of 3 inches, yields 45 in2.

Example Question #4 : How To Find The Area Of A Rectangle

A rectangle’s base is twice its height.  If the base is 8” long, what is the area of the rectangle?

Possible Answers:

24 in2

64 in2

32 in2

16 in2

12 in2

Correct answer:

32 in2

Explanation:

Rectangle

B = 2H

B = 8”

H = B/2 = 8/2 = 4”

Area = B x H = 8” X 4” = 32 in2

Example Question #1 : How To Find The Area Of A Rectangle

The length of a rectangle is two more than twice the width. The perimeter is 58ft. What is the area of the rectangle?

Possible Answers:

Correct answer:

Explanation:

For a rectangle,  and , where  is the length and  is the width.

Let  be equal to the width. We know that the length is equal to "two more than twice with width."

The equation to solve for the perimeter becomes .

Now that we know the width, we can solve for the length.

Now we can find the area using .

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