1. Scale Representation

7. What is Proportion?

8. A name that we give a statement that says two ratios are EQUAL

9. What is a RATIO?

10. A way to COMPARE two or more Quantities

11. Example

12. Lets compare 2x4s

13. And 2x6s

14. If we have (2) 2x4s and (3) 2x6s

15. we have (2) groups of lumber

16. One group containing (2) pieces and one containing (3) pieces

17. Lets compare 2x4s to 2x6s

18. (2) (3) Lets compare 2x4s to 2x6s

19. We can write this in different ways:

20. 2 to 3

21. 2 to 3 2:3

22. 2 to 3 2:3 2 3

23. For the purpose of this Section we will use

24. 2 3

25. So the Ratio of 2x4s to 2x6s is 2 3

26. If we compare 2x6s to 2x4s the ratio is 3 2

27. If we compare 2x6s to the total # of planks, the ratio is: 3 5

28. so what?

29. Let’s compare the length to the width of your houses

30. The ratio of length to width of your model house is 10:7

31. 10 being the length in inches and 7 being the width in inches

32. If the full size house is 14’ wide, how long is it?

33. Set up the proportion like this:

34. 10 = L

35. We cross multiply and divide by the lone soldier

36. 10 = L

37. 10 = L

38. 10 x 14 7L

39. 140 7L

41. Therefore, L=20

42. So, if the house is 14’ wide, it is 20’ long based on the ratio of 10:7

43. Are the two ratios equal? In other words are they proportionate?

44. Test by cross multiplying

45. 10 =

46. 7 x 20 = 140

47. 10 =

48. Therefore 10:7 and 20:14 are equal which means they are in proportion

49. Let’s try shall we?