Whole Number Arithmetic Rounding and estimating

Round to the nearest whole number

Round to one decimal place

Round to two decimal places

The reading 4.1 kg, has two significant figures.

The width of the footpath is 1.81m (to the nearest cm)

How many significant figures?

Complete this table Rounded widthSignificant Figures

Complete this table Rounded widthSignificant Figures

Round to one significant figure

How many significant figures?

How many significant figures?

How many significant figures?

The length of this pencil is 83 mm to the nearest mm. 83 mm has been rounded to two significant figures. 83 mm = m m also has two significant figures.

How many significant figures?

Exercise 9 Rounding

Round the lengths of N. Z. Rivers to the nearest 10 Km. Waikato Clutha Wanganui Taieri Rangitiki Waitaki

Round the lengths of N. Z. Rivers to the nearest 10 Km. Waikato Clutha Wanganui Taieri Rangitiki Waitaki 425 = = = = = = 210

Round the heights of N. Z. Mountains to the nearest 100 m. Cook Tasman Ruapehu Taranaki Ngauruhoe Tongariro

Round the heights of N. Z. Mountains to the nearest 100 m. Cook Tasman Ruapehu Taranaki Ngauruhoe Tongariro 3764 = = = = = = 2000

Round the areas of N. Z. Lakes to the nearest 1000 ha. Taupo Te Anau Wakatipu Wanaka Manapouri Hawea

Round the areas of N. Z. Lakes to the nearest 1000 ha. Taupo Te Anau Wakatipu Wanaka Manapouri Hawea = = = = = =

Round the areas of N. Z. Regions correct to 2 significant figures. Northland Auckland Waikato Bay of Plenty Gisborne Hawkes' Bay Taranaki Manawatu - Wanganui Wellington

Round the areas of N. Z. Regions correct to 2 significant figures. Northland Auckland Waikato Bay of Plenty Gisborne Hawkes' Bay Taranaki Manawatu - Wanganui Wellington = = = = = = = = = 8 100

Round the population of N. Z. Regions correct to 3 significant figures. Nelson Tasman Marlborough West Coast Canterbury Otago Southland New Zealand

Round the population of N. Z. Regions correct to 3 significant figures. Nelson Tasman Marlborough West Coast Canterbury Otago Southland New Zealand = = = = = = = =

This table shows the population of Auckland's 4 cities rounded to the nearest Copy down and complete the table. CityPopulationMin. PopMax. Pop North Shore Waitakere Auckland Manukau

This table shows the population of Auckland's 4 cities rounded to the nearest Copy down and complete the table. CityPopulationMin. PopMax. Pop North Shore Waitakere Auckland Manukau

Exercise 10 Approximate Calculations

Oral examples - 1 a. 90 x 6 b. 90 x 60 c. 900 x 60 d. 900 x

Oral examples - 2 a. 80 x 5 b. 80 x 50 c. 800 x 50 d. 800 x

Oral examples - 3 = 50

Oral examples - 3 = 50

Oral examples - 3 = 500

Oral examples - 3 = 500

Oral examples - 4 = 200

Oral examples - 4 = 200

Oral examples - 4 = 2000

Oral examples - 4 = 2000

Written examples 1.80 x x x x

Written examples x x x x

9. = 50

10. = 50

11. = 500

12. = 500

13. = 200

14. = 20

15. = 2000

16. = 2000

Estimation Answers are not exact

Exercise x x x x x x x x x 20 ≈ x 30 ≈ x 40 ≈ x 50 ≈ x 20 ≈ x 30 ≈ x 40 ≈ x 50 ≈ 45000

25. ≈ 5

26. ≈ 2

27. ≈ 4

28. ≈ 3

29. ≈ 40

30. ≈ 30

31. ≈ 20

32. ≈ 50

33. ≈ 400

34. ≈ 2500

35. ≈

36. ≈

37. ≈ 10

38. ≈ 20

39. ≈ 30

40. ≈ 100

41. ≈ 40

42. ≈ 20

43. ≈ 60

44. ≈ 30

45. ≈ 2

46. ≈ 4

47. ≈ 6

48. ≈ 3

49. ≈ 8 000

50. ≈

51. ≈

52. ≈

53. The sun is 150 million kilometres from the earth. Light travels a distance of kilometres every second. Find, in seconds, how long it takes light from the sun to reach the earth.

53. The sun is 150 million kilometres from the earth. Light travels a distance of kilometres every second. Find, in seconds, how long it takes light from the sun to reach the earth.

54. The earth travels 958 million kilometres in its orbit around the sun each year (365 days). By rounding off each number correct to 1 significant figure calculate how far the earth travels in 1 hour.

54. The earth travels 958 million kilometres in its orbit around the sun each year (365 days). By rounding off each number correct to 1 significant figure calculate how far the earth travels in 1 hour.

55. Repeat question 54 only use a calculator to do the actual calculation. (Round off your answer correct to 2 significant figures.)

55. Repeat question 54 only use a calculator to do the actual calculation. (Round off your answer correct to 2 significant figures.) km

56. Use a calculator to help you find how many days there are in 1 million seconds. (Round off your answer correct to 3 significant figures.)

56. Use a calculator to help you find how many days there are in 1 million seconds. (Round off your answer correct to 3 significant figures.) 11.6 days

Making Estimates Continued

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