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Rounding
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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
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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
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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
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The reading 4.1 kg, has two significant figures.
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The width of the footpath is 1.81m (to the nearest cm)
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How many significant figures?
The width of the footpath is 1.81m (to the nearest cm)
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Complete this table Rounded width Significant Figures 1.81 2 1
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Complete this table Rounded width Significant Figures 1.81 3 1.8 2 1
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Round to one significant figure
7.56 2.7 4.6 10.6 8 3 5 10
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How many significant figures?
9.6 2.5 55.1 1.26 22.4 178.3 8.75 3.24 2 3 4
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How many significant figures?
46.81 3.808 4.077 71.08 83.881 4 5 6
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How many significant figures?
400.00 40.0 1.4 1.40 1.400 10.0 1.50 100.00 5 3 2 4
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The length of this pencil is 83 mm to the nearest mm.
83 mm has been rounded to two significant figures. 83 mm = m 0.083 m also has two significant figures.
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How many significant figures?
0.061 0.007 0.46 0.070 0.0700 0.0074 2 1 3 4
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Exercise 9 Rounding
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Round the lengths of N. Z. Rivers to the nearest 10 Km.
Waikato Clutha Wanganui Taieri Rangitiki Waitaki 425 322 290 288 241 209
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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
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Round the heights of N. Z. Mountains to the nearest 100 m.
Cook Tasman Ruapehu Taranaki Ngauruhoe Tongariro 3764 3498 2797 2518 2291 1968
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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
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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
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Round the areas of N. Z. Lakes to the nearest 1000 ha.
Taupo Te Anau Wakatipu Wanaka Manapouri Hawea = = = = = =
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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
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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 = 5 600 = 5 600 = = 8 351 = 8 400 = 7 273 = 7 300 = 8 124 = 8 100
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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 97 100
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Round the population of N. Z. Regions correct to 3 significant figures.
Nelson Tasman Marlborough West Coast Canterbury Otago Southland New Zealand = = = = = = = =
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This table shows the population of Auckland's 4 cities rounded to the nearest Copy down and complete the table. City Population Min. Pop Max. Pop North Shore Waitakere Auckland Manukau
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This table shows the population of Auckland's 4 cities rounded to the nearest Copy down and complete the table. City Population Min. Pop Max. Pop North Shore Waitakere Auckland Manukau
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Approximate Calculations
Exercise 10 Approximate Calculations
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Oral examples - 1 a. 90 x 6 b. 90 x 60 c. 900 x 60 d. 900 x 600 540
5400 54 000
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Oral examples - 2 a. 80 x 5 b. 80 x 50 c. 800 x 50 d. 800 x 500 400
4000 40 000
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Oral examples - 3 = 50
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Oral examples - 3 = 50
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Oral examples - 3 = 500
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Oral examples - 3 = 500
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Oral examples - 4 = 200
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Oral examples - 4 = 200
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Oral examples - 4 = 2000
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Oral examples - 4 = 2000
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Written examples 80 x 7 x 70 x 70 x700 560 5600 56 000
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Written examples x 5 x 50 x 50 x 500 200 2000 20 000
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9. = 50
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10. = 50
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11. = 500
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12. = 500
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13. = 200
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14. = 20
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15. = 2000
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16. = 2000
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Estimation Answers are not exact
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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
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25. ≈ 5
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26. ≈ 2
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27. ≈ 4
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28. ≈ 3
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29. ≈ 40
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30. ≈ 30
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31. ≈ 20
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32. ≈ 50
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33. ≈ 400
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34. ≈ 2500
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35. ≈
63
36. ≈
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37. ≈ 10
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38. ≈ 20
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39. ≈ 30
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40. ≈ 100
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41. ≈ 40
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42. ≈ 20
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43. ≈ 60
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44. ≈ 30
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45. ≈ 2
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46. = 4
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47. = 6
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48. = 3
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49. = 8000
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50. = 27000
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51. =
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52. =
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Making Estimates Continued
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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
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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
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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
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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
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Fill the gaps Item Total cost Quantity Estimated unit cost Shorts
64.91 7 Books 47.99 8 Heaters 3385 9 Fridges 6725
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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
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Fill the gaps Item Total cost Quantity Estimated unit cost Watches
2225 51 Shoes 4309 78 Calculator 2683 92 Trousers 3416 83
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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
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Exercise 12
90
1. = 2
91
2. = 3
92
3. = 10
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4. = 100
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5. = 2
95
6. = 10
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7. = 2
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8. = 2
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9. = 4
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10. = 8
100
13.
101
14.
102
15.
103
16.
104
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105
18.
106
19.
107
20.
108
21.
109
22.
110
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111
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112
25.
113
26.
114
27.
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