Student Resources—746
Student Resources—746
Student Resources—746
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Use Geometry<br />
The branch of mathematics that deals<br />
with the measurement, properties, and relationships<br />
of points, lines, angles, surfaces,<br />
and solids is called geometry.<br />
Perimeter The perimeter (P) is the distance<br />
around a geometric figure. To find the perimeter<br />
of a rectangle, add the length and width<br />
and multiply that sum by two, or 2(l w). To<br />
find perimeters of irregular figures, add the<br />
length of the sides.<br />
Example 1 Find the perimeter of a rectangle that is<br />
3 m long and 5 m wide.<br />
Step 1 You know that the perimeter is 2 times the<br />
sum of the width and length.<br />
P 2(3 m 5 m)<br />
Step 2 Find the sum of the width and length.<br />
P 2(8 m)<br />
Step 3 Multiply by 2.<br />
P 16 m<br />
The perimeter is 16 m.<br />
Example 2 Find the perimeter of a shape with sides<br />
measuring 2 cm, 5 cm, 6 cm, 3 cm.<br />
Step 1 You know that the perimeter is the sum of all<br />
the sides.<br />
P 2 5 6 3<br />
Step 2 Find the sum of the sides.<br />
P 2 5 6 3<br />
P 16<br />
The perimeter is 16 cm.<br />
Practice Problem Find the perimeter of a rectangle<br />
with a length of 18 m and a width of 7 m.<br />
Practice Problem Find the perimeter of a triangle<br />
measuring 1.6 cm by 2.4 cm by 2.4 cm.<br />
Math Skill Handbook<br />
Area of a Rectangle The area (A) is the<br />
number of square units needed to cover<br />
a surface. To find the area of a rectangle,<br />
multiply the length times the width, or<br />
l w. When finding area, the units also are<br />
multiplied. Area is given in square units.<br />
Example Find the area of a rectangle with a length<br />
of 1 cm and a width of 10 cm.<br />
Step 1 You know that the area is the length multiplied<br />
by the width.<br />
A (1 cm 10 cm)<br />
Step 2 Multiply the length by the width. Also multiply<br />
the units.<br />
A 10 cm 2<br />
The area is 10 cm 2 .<br />
Practice Problem Find the area of a square whose<br />
sides measure 4 m.<br />
Area of a Triangle To find the area of a<br />
triangle, use the formula:<br />
A 1<br />
(base height)<br />
2<br />
The base of a triangle can be any of its sides.<br />
The height is the perpendicular distance from<br />
a base to the opposite endpoint, or vertex.<br />
Example Find the area of a triangle with a base of<br />
18 m and a height of 7 m.<br />
Step 1 You know that the area is 1<br />
the base times<br />
2<br />
the height.<br />
A 1<br />
(18 m 7 m)<br />
2<br />
Step 2 Multiply 1<br />
by the product of 18 7. Multiply<br />
2<br />
the units.<br />
A 1<br />
2 (126 m2 )<br />
A 63 m2 The area is 63 m 2 .<br />
Practice Problem Find the area of a triangle with a<br />
base of 27 cm and a height of 17 cm.<br />
MATH SKILL HANDBOOK 783<br />
Math Skill Handbook
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