This document provides formulas for calculating the perimeter and area of common shapes like squares, rectangles, triangles, parallelograms, and circles. It explains that the perimeter is the distance around the outside of a shape and is found by adding all the side lengths. The area is the space inside the shape and is measured in square units. Formulas provided include: Perimeter of squares and rectangles = 2(Length + Width) Area of squares and rectangles = Length x Width Area of triangles = 1/2 x Base x Height Area of circles = π x Radius2

1. Formulas for Geometry Mr. Ryan Visit www.worldofteaching.com for more free powerpoints

2. Don’t Get Scared!!! Evil mathematicians have created formulas to save you time. But, they always change the letters of the formulas to scare you!

3. Perimeter Any shape’s “perimeter” is the outside of the shape…like a fence around a yard.

4. Perimeter To calculate the perimeter of any shape, just add up “each” line segment of the “fence”.

5. Perimeter Triangles have 3 sides…add up each sides length. 8 8 8 8+8+8=24 The Perimeter is 24

6. Perimeter A square has 4 sides of a fence 12 12 12 12 12+12+12+12=48

7. Perimeter Sometimes, problems may only give you two measurements for a square or rectangle. No problem…use the formula for squares/rectangles (only!)

8. Remember Squares ALL sides are equal…so if they give you one side, you know ALL the sides Length=the Largest side If they “leave” numbers out, they are equal to their opposite side. If they give you the bottom of a square/rectangle type shape then the top is the same

9. The Same!! If the bottom is 15…the top is… 15

10. Square/Rectangle Formula Perimeter=2(Length+Width) P= 2(25+14) P=2(20+20) P= 50+28 P=40+40 P= 78 P=80 14 25 20

11. Other shapes Just add up EACH segment 10 8 sides, each side 10 so 10+10+10+10+10+10+10+10=80

12. Odd shapes Count ALL sides Remember if one side blank, it’s equal to its opposite 25 15 5 25+25=50 (for Length) 15+5+15+5=40 (for Width) Perimeter=90

13. Area Area is the ENTIRE INSIDE of a shape It is always measured in “squares” (sq. inch, sq ft)

14. AREA Square units means that “that” many squares fit inside that shape (if measured in feet…it’s feet…if meters…it’s meters. In this example the area is 4 square units…note 4 squares fit) 2 units (ft, in, m) 2 3 4 1

15. Area of Squares/Rectangles Length x Width=Area 2 Length(2) xWidth(2) = 4 square units

16. Parallelogram Area Same idea as squares & rectangles, but they change the words to Base (length:bottom of shape) and height (width)

17. Parallelogram Area Area=Base x Height (Area=length x width) BASE (length) Height (width) 8 5 Base 8 x Height 5 = Area 40 The diagonal line is NOT the height!!!

18. REAL formula for area of squares Area= S^2 Area= Side x Side (side squared) (just a different way of saying length x width) Side one Side two

19. Different Names/Same idea Length x Width = Area Side x Side = Area Base x Height = Area

20. Area of a Triangle ½ Base x Height = Area (It’s ½ because ½ of the “square” is missing) Base Height Height Base 8 5 ½ Base x Height = Area ½ (8) x 5 = Area 4 x 5 = 20

21. Area of a Circle Pi= 3.14 Radius: from center (origin) of circle to ANY side Area= pi x (Radius x Radius)

22. Circumference of a Circle Perimeter/Circumference = pi x diameter Pi is always 3.14 Circumference is a fancy name for perimeter The diameter is a line from one side to the other side of a circle through its origin (It’s twice the radius) If the radius is 5, then the diameter is 10

23. Area of a circle Area = piR^2 Pi = 3.14 and R=Radius Radius 5 Area=3.14 x (5 x 5) Perimeter = 3.14 x 10

24. You’re Done Squares, rectangles and parallelograms area are almost the same (LxW) Triangles are ½ cause your missing ½ Circles have fancy names, but just follow the formula

25.  For most tests you will have the formulas given to you. Just remember which one to use for which shape and you’ll do fine.