How to find the area of a figure

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HSPT Math › How to find the area of a figure

Questions 1 - 10
1

What is the area of the figure below?

11

Explanation

To find the area of the figure above, we need to slip the figure into two rectangles.

11.5

Using our area formula, , we can solve for the area of both of our rectangles

To find our final answer, we need to add the areas together.

2

What is the area of the figure below?

12

Explanation

To find the area of the figure above, we need to slip the figure into two rectangles.

12.5

Using our area formula, , we can solve for the area of both of our rectangles

To find our final answer, we need to add the areas together.

3

The ratio of the perimeter of one square to that of another square is . What is the ratio of the area of the first square to that of the second square?

Explanation

For the sake of simplicity, we will assume that the second square has sidelength 1; Then its perimeter is , and its area is .

The perimeter of the first square is , and its sidelength is . The area of this square is therefore .

The ratio of the areas is therefore .

4

Rectangle

Give the area of the above rectangle in square feet.

Explanation

Since 1 yard = 3 feet, multiply each dimension by 3 to convert from yards to feet:

Use the area formula, substituting :

square feet

5

The area of the square is 81. What is the sum of the lengths of three sides of the square?

Explanation

A square that has an area of 81 has sides that are the square root of 81 (side2 = area for a square). Thus each of the four sides is 9. The sum of three of these sides is .

6

A trapezoid has height 32 inches and bases 25 inches and 55 inches. What is its area?

Explanation

Use the following formula, with :

7

What is the area of the triangle?

Question_11

Explanation

Area of a triangle can be determined using the equation:

8

What is the area of the figure below?

11

Explanation

To find the area of the figure above, we need to slip the figure into two rectangles.

11.5

Using our area formula, , we can solve for the area of both of our rectangles

To find our final answer, we need to add the areas together.

9

A square is 9 feet long on each side. How many smaller squares, each 3 feet on a side can be cut out of the larger square?

Explanation

Each side can be divided into three 3-foot sections. This gives a total of squares. Another way of looking at the problem is that the total area of the large square is 81 and each smaller square has an area of 9. Dividing 81 by 9 gives the correct answer.

10

A square with a side length of 4 inches is inscribed in a circle, as shown below. What is the area of the unshaded region inside of the circle, in square inches?

Act_math_01

8π - 16

4π-4

8π-4

2π-4

8π-8

Explanation

Using the Pythagorean Theorem, the diameter of the circle (also the diagonal of the square) can be found to be 4√2. Thus, the radius of the circle is half of the diameter, or 2√2. The area of the circle is then π(2√2)2, which equals 8π. Next, the area of the square must be subtracted from the entire circle, yielding an area of 8π-16 square inches.

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