Chap 3: Reasonable Estimation?

Textbook: Exercise 3.3 (p69)

(a) 5837 + 985 = (est) 7000

(b) 347 - 482 + 650 = (est) -500

(c) 23.92 x 4.801 = (est) 1200

(e) 62.47 x 0.093 ÷ 0.00217 = (est) 40000

In the comments,
  • Write down if each estimated value is reasonable?
  • Justify your answer with working.

23 comments:

  1. (a) 5837+ 985≈ (est)7000
    (b)347-482+650≈ (est)500
    (c)23.92x4.801≈ (est)120
    (e)60x0.1÷0.002≈(est)3000

    (b),(c) and (e) are wrong

    ReplyDelete
  2. This comment has been removed by the author.

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  3. The estimated answers of b, c and e are unreasonable.

    b should be 347-482+650≈300-500+700(1SF)
    =500

    c should be 23.92 X 4.801≈24X5 (1SF)
    =120

    e should be 62.47X0.093÷0.00217≈62X0.09÷0.002(1SF)
    =2.835

    ReplyDelete
  4. This comment has been removed by the author.

    ReplyDelete
  5. (a) 5837 + 985 ≈ 6000 + 1000
    = 7000

    Yes, (a) is reasonable.

    (b) 347 - 482 + 650 ≈ 300 - 500 + 700
    = -200 + 700
    = -500

    Yes, (b) is reasonable.

    (c) 23.92 x 4.801 ≈ 24 x 5
    = 120

    No, (c) is not reasonable.

    (e) 62.47 x 0.093 ÷ 0.00217 ≈ 62 x 0.09 ÷ 0.002
    = 5.58 ÷ 0.002
    = 2.790

    No, (e) is not reasonable.

    ReplyDelete
  6. (a) 5837 + 985 = 6822 (reasonable)
    (b) 347 - 483 + 650
    ≈ 135 + 650
    515(not reasonable )
    (c) 23.92 x 4.801 = 114.83992(not reasonable)
    (d) 62.47 x 0.093 ÷ 0.00217 = 2 677 28571 (not reasonable)

    ReplyDelete
  7. (a)5837 + 985 = 6822 (reasonable)
    (b)347 - 482 + 650
    =-135 + 650
    =515 (not reasonable)
    (c)23.92 x 4.801
    =114.83992 (not reasonable)
    (d)62.47 x 0.093 ÷ 0.00217 = 2 677.28571 (not reasonable)

    ReplyDelete
  8. a)5837 + 985=(est) 6000 + 1000
    = 7000
    Therefore, the estimated value of (a) is reasonable.

    b)347 - 482 + 650≈(est) 300 - 500 + 700
    =(-200) + 700
    =500
    The estimated value of (b) is not reasonable; the answer should be (+)500 instead of -500.

    c) 23.92 x 4.801≈(est) 20 x 5
    =100
    The estimated value of (c) is not reasonable; the answer is 100 instead of 1200.

    e) 62.47 x 0.093 ÷ 0.00217≈(est) 60 x 0.09 ÷ 0.002
    = 5.4 ÷ 0.002
    =2700
    The estimated value of (e) is not reasonable; the answer is 2700 instead of 40 000.

    ALL answers are rounded off to the 1st significant number.

    ReplyDelete
  9. a)5837 + 985 ≈ 6000 + 1000
    = 7000
    b)Not reasonable because
    347 - 482 + 650 ≈ 300 - 500 + 700
    = 500
    c) Not reasonable because
    23.92 x 4.801 ≈24 x 4
    =96
    d)62.47 x 0.093 ÷ 0.00217 ≈ 62 x 0.1
    = 6.2

    ReplyDelete
  10. No, (b), (c), and (e) is not reasonable. (a) is reasonable.

    (a) 5837+985≈6000+1000
    =7000

    (b) 347-482+650

    ReplyDelete
  11. I think that (a) is reasonable as the sum is rounded off to the nearest thousands.
    I think that (b) is unreasonable as the estimated answer is suppose to be 500(300-500+700) and not -500.
    I think that (c) is unreasonable as the estimated answer is suppose to be 120(24x5) and not 1200.

    ReplyDelete
  12. a= Reasonable
    6000+1000=7000
    b=Unreasonable
    400-500+700=500
    c=Unreasonable
    20x5=100
    e=Unreasonable
    60x0.09÷0.002=2700

    ReplyDelete
  13. a) 5837 + 985≈6000+1000
    =7000
    (b) 347 - 482 + 650≈300-500+700
    =500
    (c) 23.92 x 4.801≈20 x 5
    =100
    (e) 62.47 x 0.093 ÷ 0.00217 ≈ 60 x 0.09 ÷ 0.002
    = 5.4 ÷ 0.002

    ReplyDelete
  14. (a) It is reasonable as the numbers are rounded off to 1 significant figure.
    (b) It is unreasonable.
    347 - 482 + 650 ≈ 300 - 500 + 700
    = -200+700
    = 500
    The answer is not -500 but 500.
    (c) 23.92 x 4.801 ≈ 20 x 5
    = 100
    (e) 62.47 x 0.093 0.00217 ≈ 60 x 0.09 ÷ 0.002
    = 2790

    ReplyDelete
  15. (a) Exact value: 5837 + 985 = 6822 (reasonable)

    (b) Exact value: 347-482+650 = 515 (not reasonable)

    (c) Exact value : 23.92 x 4.801 = 114.83992 (not reasonable)

    (d) 62.47 x 0.093 ÷0.00217 = 2677.28571 (not reasonable)

    chengngee

    ReplyDelete
  16. a) reasonable

    Working:

    a) 5837+ 985 ≈ 6000+ 1000
    = 7000

    b) unreasonable

    Working

    b) 347-482+650 ≈ 300-500+700
    = 500

    Part 1

    ReplyDelete
  17. It is reasonable.
    5837+985≈6000+1000
    =7000
    It is not reasonable.
    347 - 482 + 650 ≈300-500+700
    = 500
    It is not reasonable.
    23.92 x 4.801≈20×5
    =100
    62.47 x 0.093 ÷ 0.00217≈60×0.09÷0.002
    = 2700

    ReplyDelete
  18. a) reasonable

    5837+985≈6000+1000
    =7000

    b) reasonable
    347-482+650≈ 300-500+700
    = (-200) + 700
    =-900

    c) unreasonable

    23.92 x 4.801≈ 24x5
    =120

    e) unreasonable

    62.47x0.093÷0.00217≈ 62x0.1÷0.002
    = 6.2÷0.002
    = 3100

    ReplyDelete
  19. (a) 5837+985≈ 6000+1000
    = (est)7000
    (b) 347-482+650≈ 300-500+700
    = (est) 500
    (c) 23.92x4.801≈ 24x5
    = (est) 120
    (e) 62.47x0.093÷0.00217≈ 62x0.1÷0.002
    = (est) 3100

    (b), (c) and (e) are not reasonable.

    ReplyDelete
  20. Part 2

    c) unreasonable

    Workings:23.92x 4.801≈24x 5
    =120


    e) unreasonable

    Workings: 62.47x0.093≈ 60x0.1÷0.002
    =3000

    ReplyDelete
  21. (a) 5837 + 985 = (est) 7000
    5837 + 985 ≈ 6000 + 1000
    = 7000

    (b) 347 - 482 + 650 = (est) -500
    347 - 482 + 650 ≈300-500+700
    = 500

    (c) 23.92 x 4.801 = (est) 1200
    23.92 x 4.801 ≈24 x 5
    = 120

    (e) 62.47 x 0.093 ÷ 0.00217 = (est) 40000
    62.47 x 0.093 ÷ 0.00217 ≈ 60 x 0.09 ÷ 0.002
    =2700

    ReplyDelete
  22. Follow-up:
    (a) 5837 + 985 = 6822

    (b) 347 - 482 + 650 = 515

    (c) 23.92 x 4.801 ≈ 114

    (e) 62.47 x 0.093 ÷ 0.00217 ≈ 2677

    As comparing to the estimation, (a) is reasonable & (b),(c),(d) is not reasonable.

    ReplyDelete
  23. (a) is reasonable as both numbers are rounded off to 1 significant figure.
    (b) It is not reasonable.
    347-482+650≈-135+650
    =515
    (c) 23.92 x 4.801 ≈ 114(unreasonable)
    (e) 62.47 x 00.093 ÷ 0.00217≈ 2677(unreasonable)

    ReplyDelete