Rounding

Round to the nearest whole number 621.8 19.02 57.04 98.63 1.03 610.8 519.6 622 19 57 99 1 611 520

Round to one decimal place 19.023 57.046 81.774 89.522 1.03 2.59 49.97 19.0 57.0 81.8 89.5 1.0 2.6 50.0

Round to two decimal places 1.902 5.704 0.1036 2.974 0.006 3.899 0.003 1.90 5.70 0.10 2.97 0.01 3.90 0.00

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

Complete this table Rounded width Significant Figures 1.81 2 1

Complete this table Rounded width Significant Figures 1.81 3 1.8 2 1

Round to one significant figure 7.56 2.7 4.6 10.6 8 3 5 10

How many significant figures? 9.6 2.5 55.1 1.26 22.4 178.3 8.75 3.24 2 3 4

How many significant figures? 46.81 3.808 4.077 71.08 83.881 778.049 4 5 6

How many significant figures? 400.00 40.0 1.4 1.40 1.400 10.0 1.50 100.00 5 3 2 4

The length of this pencil is 83 mm to the nearest mm. 83 mm has been rounded to two significant figures. 83 mm = 0.083 m 0.083 m also has two significant figures.

How many significant figures? 0.061 0.007 0.00061 0.46 0.070 0.0700 0.0074 0.07006 2 1 3 4

Exercise 9 Rounding

Round the lengths of N. Z. Rivers to the nearest 10 Km. Waikato Clutha Wanganui Taieri Rangitiki Waitaki 425 322 290 288 241 209

Round the lengths of N. Z. Rivers to the nearest 10 Km. Waikato Clutha Wanganui Taieri Rangitiki Waitaki 425 = 430 322 = 320 290 = 290 288 = 290 241 = 240 209 = 210

Round the heights of N. Z. Mountains to the nearest 100 m. Cook Tasman Ruapehu Taranaki Ngauruhoe Tongariro 3764 3498 2797 2518 2291 1968

Round the heights of N. Z. Mountains to the nearest 100 m. Cook Tasman Ruapehu Taranaki Ngauruhoe Tongariro 3764 = 3800 3498 = 3500 2797 = 2800 2518 = 2500 2291 = 2300 1968 = 2000

Round the areas of N. Z. Lakes to the nearest 1000 ha. Taupo Te Anau Wakatipu Wanaka Manapouri Hawea 60 606 34 447 29 267 19 166 14 245 11 914

Round the areas of N. Z. Lakes to the nearest 1000 ha. Taupo Te Anau Wakatipu Wanaka Manapouri Hawea 60 606 = 61 000 34 447 = 34 000 29 267 = 29 000 19 166 = 19 000 14 245 = 14 000 11 914 = 12 000

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 13 941 5 600 25 598 12 447 8 351 14 164 7 273 22 215 8 124

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 13 941 = 14 000 5 600 = 5 600 25 598 = 26 000 12 447 = 12 000 8 351 = 8 400 14 164 = 14 000 7 273 = 7 300 22 215 = 22 000 8 124 = 8 100

Round the population of N. Z. Regions correct to 3 significant figures. Nelson Tasman Marlborough West Coast Canterbury Otago Southland New Zealand 40 279 37 973 38 397 32 512 468 040 185 083 97 100 3 618 302

Round the population of N. Z. Regions correct to 3 significant figures. Nelson Tasman Marlborough West Coast Canterbury Otago Southland New Zealand 40 279 = 40 300 37 973 = 38 000 38 397 = 38 400 32 512 = 32 500 468 040 = 468 000 185 083 = 185 000 97 100 = 97 100 3 618 302 = 3 620 000

This table shows the population of Auckland's 4 cities rounded to the nearest 1000. Copy down and complete the table. City Population Min. Pop Max. Pop North Shore 172 000 171 500 172 499 Waitakere 156 000 Auckland 346 000 Manukau 254 000

This table shows the population of Auckland's 4 cities rounded to the nearest 1000. Copy down and complete the table. City Population Min. Pop Max. Pop North Shore 172 000 171 500 172 499 Waitakere 156 000 155 500 156 499 Auckland 346 000 345 500 346 499 Manukau 254 000 253 500 254 499

Approximate Calculations Exercise 10 Approximate Calculations

Oral examples - 1 a. 90 x 6 b. 90 x 60 c. 900 x 60 d. 900 x 600 540 5400 54 000 540 000

Oral examples - 2 a. 80 x 5 b. 80 x 50 c. 800 x 50 d. 800 x 500 400 4000 40 000 400 000

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 80 x 7 2. 80 x 70 3. 800 x 70 4. 800 x700 560 5600 56 000 560 000

Written examples 5. 40 x 5 6. 40 x 50 7. 400 x 50 8. 400 x 500 200 2000 20 000 200 000

9. = 50

10. = 50

11. = 500

12. = 500

13. = 200

14. = 20

15. = 2000

16. = 2000

Estimation Answers are not exact

Exercise 10 91 x 18 82 x 29 73 x 36 64 x 47 621 x 19 685 x 32 817 x 38 893 x 51 90 x 20 ≈ 1800 80 x 30 ≈ 2400 70 x 40 ≈ 2800 60 x 50 ≈ 3000 600 x 20 ≈ 12000 600 x 30 ≈ 18000 800 x 40 ≈ 32000 900 x 50 ≈ 45000

25. ≈ 5

26. ≈ 2

27. ≈ 4

28. ≈ 3

29. ≈ 40

30. ≈ 30

31. ≈ 20

32. ≈ 50

33. ≈ 400

34. ≈ 2500

35. ≈ 90 000

36. ≈ 160 000

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. = 8000

50. = 27000

51. = 160000

52. = 810000

Making Estimates Continued

Fill the gaps Item Unit cost ($) Quantity Estimated cost ($) Apples 1.83 4 Chickens 8.95 9 Calculator 16.85 7 DVD 9.95 10

Fill the gaps Item Unit cost ($) Quantity Estimated cost ($) Apples 1.83 4 8 Chickens 8.95 9 81 Calculator 16.85 7 140 DVD 9.95 10 100

Fill the gaps Item Unit cost ($) Quantity Estimated cost ($) Hairdryer 23.15 38 Toaster 47.95 27 Shorts 14.85 74 Chairs 83.75 65

Fill the gaps Item Unit cost ($) Quantity Estimated cost ($) Hairdryer 23.15 38 800 Toaster 47.95 27 1500 Shorts 14.85 74 700 Chairs 83.75 65 5600

Fill the gaps Item Total cost Quantity Estimated unit cost Shorts 64.91 7 Books 47.99 8 Heaters 3385 9 Fridges 6725

Fill the gaps Item Total cost Quantity Estimated unit cost Shorts 64.91 7 9 Books 47.99 8 6 Heaters 3385 400 Fridges 6725 1000

Fill the gaps Item Total cost Quantity Estimated unit cost Watches 2225 51 Shoes 4309 78 Calculator 2683 92 Trousers 3416 83

Fill the gaps Item Total cost Quantity Estimated unit cost Watches 2225 51 40 Shoes 4309 78 50 Calculator 2683 92 30 Trousers 3416 83

Exercise 12

1. = 2

2. = 3

3. = 10

4. = 100

5. = 2

6. = 10

7. = 2

8. = 2

9. = 4

10. = 8

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