Success step english 5 pps

Square

Measuring the area and perimeter of a square is basi￾cally the same as a rectangle, only the length and width

are the same measurement.

Area: side × side

Perimeter: side × 4

Triangle

Remember that a triangle is half a rectangle.

Area:

1

2

b × h. Multiply the height and the base.

Since the triangle is half, divide by two. Note:

The height of a triangle is not always one of the

sides. For example, in triangle ABC which fol￾lows, side AB is not the height, BD is the height.

AC is the base. To find the area, ignore all the

numbers but the base and the height. The base

can be found by adding 4 and 8: 4 + 8 = 12. The

height is 5.

1

2

× 5 × 12 =

6

2

0

or 30.

Perimeter: Add the sides all around: 12 + 6 + 9 = 27

Circle

The diameter of a circle goes from one point on the

circle, through the middle, and all the way across to

another point on the circle. The radius (r) is half of the

diameter. When working with π, consider the follow￾ing: The symbol π is usually found in the answers so

you don’t have to worry about converting it to a num￾ber. But if π is not found in the answers, and the ques￾tion calls for an approximate answer, substitute 3 for π.

The question may tell you to use

2

7

2

or 3.14.

Area: πr2. Square the radius and look at the answers.

If π is not found in the answers, multiply by 3. In

the example above, A = π42 or 16π.

Circumference: 2πr. Circumference is to a circle what

perimeter is to a rectangle. Multiply the radius by

2 and look for the answers. If π is not in the

answer choices, multiply by 3. In the example

above, the circumference is 2π4, or 8π.

Other Areas

Cut the figure into pieces, find the area of each, and

add. If you’re asked to find the area of a figure with a

piece cut out of it, find the area of the whole figure,

find the area of the piece, and subtract.

Other Perimeters

For any perimeter, just add the outside lengths all the

way around.

Practice

8. Find the area of a circle with a diameter of 6.

a. 36π

b. 24π

c. 16π

d. 9π

e. 6π

–CBEST MINI-COURSE–

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