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Estimation in numbers and measurement

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Form 1 Mathematics Chapter 5 Lesson requirement Textbook 1A Workbook 1A Notebook (and folder) Before lessons start Desks in good order! No rubbish around! – PowerPoint PPT presentation

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Title: Estimation in numbers and measurement


1
Estimationin numbers and measurement
  • Form 1 Mathematics
  • Chapter 5

2
Reminder
  • Lesson requirement
  • Textbook 1A
  • Workbook 1A
  • Notebook (and folder)
  • Before lessons start
  • Desks in good order!
  • No rubbish around!

3
Estimation (p.189)
  • An estimation is a rough guess on the actual
    values.
  • It does not represent the real answer.
  • In real life, we seldom bring a calculator with
    us. So, we can use estimation to make some
    decisions.
  • To get a better estimation, we need some
    techniques to round off a number.

4
Rounding off a number (????)
  • Consider the unwanted leftmost digit.
  • If greater or equal to 5, add 1 to left digit
    next to it.
  • Otherwise, leave left digit next to it unchanged.
  • E.g. 21.29 15.78 30.97 3.24 5.86
  • Rounding off to nearest tenth digit (???)
  • Rounding off to nearest unit (??)
  • Rounding off to nearest ten digit (??)

5
Rounding off (????)
  • Rounding off to nearest tenth digit
  • 21.29 15.78 30.97 3.24 5.86? 21.3
    15.8 31.0 3.2 5.9 77.2
  • Rounding off to nearest unit (or one)
  • 21.29 15.78 30.97 3.24 5.86? 21
    16 31 3 6 77
  • Rounding off to nearest ten digit
  • 21.29 15.78 30.97 3.24 5.86? 20
    20 30 0 10 80
  • The actual answer is 77.14

6
Front-end method (????)
  • Consider the leftmost digit.
  • Leave the first leftmost digit
  • Other change to 0!
  • E.g. 21.29 15.78 30.97 3.24 5.86
  • 21.29 15.78 30.97 3.24 5.86? 20.00
    10.00 30.00 3.00 5.00 20 10 30 3
    5 68 (Actual answer is 77.14)

7
Rounding up (???)
  • Consider the unwanted digits.
  • All change to 0
  • Add 1 to left digit next to them
  • E.g. 21.29 15.78 30.97 3.24 5.86
  • Rounding up to nearest tenth digit
  • Rounding up to nearest unit
  • Rounding up to nearest ten digit

8
Rounding up (???)
  • Rounding up to nearest tenth digit
  • 21.29 15.78 30.97 3.24 5.86? 21.3
    15.8 31.0 3.3 5.9 77.3
  • Rounding up to nearest unit (or one)
  • 21.29 15.78 30.97 3.24 5.86? 22
    16 31 4 6 79
  • Rounding up to nearest ten digit
  • 21.29 15.78 30.97 3.24 5.86? 30
    20 40 10 10 110
  • Actual answer 77.14. All are over-estimated.

9
Rounding DOWN (???)
  • Consider the unwanted digits.
  • All change to 0
  • Leave all left digits next to them unchanged
  • E.g. 21.29 15.78 30.97 3.24 5.86
  • Rounding down to nearest tenth digit
  • Rounding down to nearest unit
  • Rounding down to nearest ten digit

10
Rounding down (???)
  • Rounding down to nearest tenth digit
  • 21.29 15.78 30.97 3.24 5.86? 21.2
    15.7 30.9 3.2 5.8 76.8
  • Rounding down to nearest unit (or one)
  • 21.29 15.78 30.97 3.24 5.86? 21
    15 30 3 5 74
  • Rounding down to nearest ten digit
  • 21.29 15.78 30.97 3.24 5.86? 20
    10 30 0 0 60
  • Actual answer 77.14. All are under-estimated.

11
Time for Practice
  • Page 195 of Textbook 1A
  • Class Practice
  • Page 200 of Textbook 1A
  • Questions 3 6
  • Pages 93 - 94 of WB 1A
  • Questions 1 - 4
  • SHW (I)
  • Questions 1 - 8

12
Reminder
  • Lesson
  • Get ready all the time!
  • Desk
  • Be order all the time!
  • Extra Tutorial
  • Final examination less than 50

13
  • Enjoy the world of Mathematics!
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