1. Calculating Percent Increases and Decreases The Impact of Las Vegas City Growth on Lake Mead

2. Las Vegas - 1984 8 miles

3. Las Vegas - 1984 8 miles

4. Las Vegas - 1984 8 miles Length = 1.8 inches Width = 1.6 inches

5. Las Vegas - 1984 8 miles Length = 1.8 inches Width = 1.6 inches Area = length x width

6. Las Vegas - 1984 8 miles Length = 1.8 inches Width = 1.6 inches Area = 1.8 inches x 1.6 inches = 2.88 inches 2

7. How do we change from inches to miles? 1.We need to measure the scale 2.The scale says 0.5 inches = 8 miles 3.We need to multiply our area in inches by our conversion factor 2.88 inches 2 x 8 miles 2 = 46.08 0.5 inches 2 miles 2

8. Our Data Table City & YearArea in Square Miles % Change Las Vegas - 198446.08 square miles NA Las Vegas - 1994 Las Vegas - 2004

9. What’s Next? We need to measure the area of Las Vegas in 1994

10. Las Vegas - 1994 8 miles Length = 2.45 inches Width = 2 inches

11. Great!!! Now Lets Do the Following Calculate the area of the rectangle in square inches Convert the area to square miles

12. Our Data Table City & YearArea in Square Miles % Change Las Vegas - 198446.08 square miles NA Las Vegas - 199478.4 square miles Las Vegas - 2004

13. Calculate % Change for an Increase Step 1: Calculate the change (subtract old value (t1) from the new value(t2)) Step 2: Divide that change by the old value (t1) (you will get a decimal number) Step 3: Convert that to a percentage (by multiplying by 100 and adding a "%" sign) % Change = t2 – t1 x 100 t1

14. % Change in Area for Las Vegas between 1984 & 1994 Las Vegas had 70.1% change in area in 10 years % Change = 78.4 – 46.08 x 100 46.08

15. Our Data Table City & YearArea in Square Miles % Change Las Vegas - 198446.08 square miles NA Las Vegas - 199492.8 square miles70.1% Las Vegas - 2004

16. Now Lets Get all the Data for Las Vegas 2004 Calculate the area of the rectangle in square inches Convert the area to square miles Calculate % Change

17. Las Vegas - 2004 8 miles

18. Las Vegas - 2004 8 miles Length = 2.9 inches Width = 3.4 inches

19. Our Data Table City & YearArea in Square Miles % Change Las Vegas - 198446.08 square miles NA Las Vegas - 199492.8 square miles70.1% From 1984 Las Vegas - 2004157.76 square miles70% From 1994

20. Conclusion The City of Las Vegas is increasing in size by 70% every 10 years between 1984 and 2004 What impact might this be having on the area of nearby Lake Mead?

21. Lake Mead 1984 25 miles

22. What’s First? We need to calculate the area of Lake Mead in Inches.

23. Lake Mead 1984 25 miles 2.5 inches 1.75 inches Area = 2.5 inches x 1.75 inches = 4.38 inches 2

24. What’s Second? We need to convert inches 2 into miles 2 using a conversion factor

25. How do we change from inches to miles? 1.We need to measure the scale 2.The scale says 1 inch = 25 miles 3.We need to multiply our area in inches by our conversion factor 4.38 inches 2 x 25 miles 2 = 109.5 1 inches 2 miles 2

26. Our Data Table Lake & YearArea in Square Miles % Change Lake Mead - 1984109.5 square miles NA Lake Mead - 1994 Lake Mead - 2004

27. Great!!! Now Lets Do the Following for Lake Mead in 1994 Calculate the area of the rectangle in square inches Convert the area to square miles

28. Lake Mead 1994 25 miles Area = 2.4 inches x 1.75 inches = 4.2 inches 2 2.4 inches 1.75 inches

29. Our Data Table Lake & YearArea in Square Miles % Change Lake Mead - 1984109.5 square miles NA Lake Mead - 1994 105 square miles Lake Mead - 2004

30. Our Data Table Lake & YearArea in Square Miles % Change Lake Mead - 1984109.5 square miles NA Lake Mead - 1994 105 square miles Lake Mead - 2004 We’re shrinking!!! We need to calculate For a % Decrease

31. Calculate % Change for a Decrease Step 1: Calculate the change (subtract new value (t2) from the old value(t1)) Step 2: Divide that change by the old value (t1) (you will get a decimal number) Step 3: Convert that to a percentage (by multiplying by 100 and adding a "%" sign) % Change = t1 – t2 x 100 t1

32. % Change in Area for Lake Mead between 1984 & 1994 Lake Mead decreased in surface area by 4.1% in 10 years % Change = 109.5 – 105 x 100 109.5

33. What Observations Can We Make? Period in YearsLas Vegas, NevadaLake Mead, Nevada 1984 - 199470% increase in size4.1% decrease in size 1994 - 2004

34. Now Lets Get all the Data for Lake Mead in 2004 Calculate the area of the rectangle in square inches Convert the area to square miles Calculate % Change

35. Lake Mead 2004 25 miles

36. Lake Mead 2004 25 miles Area = 2.1 inches x 1.6 inches = 3.36 inches 2 2.1 inches 1.6 inches

37. Our Data Table Lake & YearArea in Square Miles % Change Lake Mead - 1984109.5 square miles NA Lake Mead - 1994 105 square miles4.1% decrease from 1984 Lake Mead - 2004 84 square miles20% decrease from 1994

38. What Observations Can We Make? Period in YearsLas Vegas, NevadaLake Mead, Nevada 1984 - 199470% increase in size4.1% decrease in size 1994 - 200470% increase in size 20% decrease in size How is the Growth of Las Vegas affecting Lake Mead?