Chap 3: Reasonable Estimation?

Textbook: Exercise 3.3 (p69)

(a) 5837 + 985 ≈ 7000
(b) 347 - 482 + 650 ≈ -500
(c) 23.92 x 4.801 ≈ 1200
(e) 62.47 x 0.093 ÷ 0.00217 ≈ 40000

In the comments,
  • Write down if each estimated value is reasonable?
  • Justify your answer with working.
When you have completed with this piece of work, proceed to AceLearning to attempt the Quizzes 03 & 04 (as Homework). You should finish them by 2359h today :D

19 comments:

  1. 5837+985≈7000 is reasonable as the numbers were rounded correctly and evaluated correctly.
    347-482+650≈-500 is not correct as it is positive
    c is incorrect as there is an extra 0
    e is incorrect as it should be 3000

    ReplyDelete
  2. a) Yes.
    5837 + 985 ≈ 6000 + 1000 ( 1 S.F. )
    = 7000 (Ans)

    b) Yes.
    347 - 482 + 650 ≈ 300 - 500 + 700 ( 1 S.F. )
    = 500 (Ans)

    c) No.
    23.92 x 4.801 ≈ 20 x 5 ( 1 S.F. )
    = 100 ( Ans )

    d) No.
    62.47 x 0.093 ÷ 0.00217 ≈ 60 x 0.1 ÷ 0.002
    = 6 ÷ 0.002
    = 3000

    Sorry if there was any errors done. : D

    ReplyDelete
  3. (a) 5837 + 985 ≈ 7000
    This answer is reasonable.
    5837 + 985
    ≈6000+1000
    =7000
    (b) 347 - 482 + 650 ≈ -500
    Tis answer is not reasonable.
    347 - 482 + 650
    ≈300-500+700
    =-200+700
    =500
    (c) 23.92 x 4.801 ≈ 1200
    This answer is not reasonable
    23.92 x 4.801
    ≈24 x 5
    =120
    d)62.47 x 0.093 ÷ 0.00217 ≈ 40000
    This answer is not reasonable
    62.47 x 0.093 ÷ 0.00217
    ≈62 x 0.1 ÷ 0.002
    =6.2 ÷ 0.002
    =0.013

    ReplyDelete
  4. a) It is reasonable. 6000 + 1000 ≠ 7000
    b)It is not reasonable. It should be 300-500+700≠500 not -500
    c) It is not reasonable. It should 24*5= 120 not 1200.
    d) It is 60*0.1÷0.002≠3000 not 40000

    ReplyDelete
  5. a) It is definitely reasonable as the answer is correct
    5837 + 985
    ≈ 6000 + 1000 (1 S.F.)
    = 7000

    b) It is not reasonable. its suppose to be 500, not (-500)
    347 - 482 + 650
    ≈ 300 - 500 + 700 (1 S.F.)
    = 500

    c) It is not reasonable as the answer is 120, not 1200.
    23.92 x 4.801
    ≈ 24 x 5 (1 S.F)
    = 120

    d) This is also unreasonable. It is 3000, not 40000.
    62.47 x 0.093 ÷ 0.00217
    ≈ 60 x 0.1 ÷ 0.002 (1 S.F)
    = 6 ÷ 0.002
    = 3000

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

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

    (b)No
    347-482+650
    ≈300-500+650
    =450

    (c)No
    23.92 x 4.801
    ≈24 x 5
    =120

    (e)No
    62.47 x 0.093÷0.00217
    ≈62 x 0.09÷0.002
    =2700

    ReplyDelete
  8. (a) Definitely yes!
    5837 + 985 ≈ 6000 + 1000
    = 7000
    ``````````````````````````````````````````````````
    (b) No.
    347 - 482 + 650 ≈ 300 - 500 + 700
    = ( - 200 ) + 700
    = 500. Not - 500
    ``````````````````````````````````````````````````
    (c) No.
    23.92 x 4.801 ≈ 24 x 5
    = 120 . Not 1200
    ``````````````````````````````````````````````````
    (e) No . 62.47 x 0.093 ÷ 0.00217 ≈ 62 x 0.09÷0.002
    =2700 . Not 40000

    ReplyDelete
  9. (a) 5837 + 985 ≈ 7000
    Yes because (a)5837+985≈6000+1000(1 S.F)=7000
    (b) 347 - 482 + 650 ≈ -500
    No, as 347-482+650≈300-500+700(1 S.F)=500
    (c) 23.92 x 4.801 ≈ 1200
    No, as 23.92 x 4.801≈24 x 5(1 S.F)=120
    (e) 62.47 x 0.093 ÷ 0.00217 ≈ 40000
    No,as 62.47 x 0.093÷0.00217≈62 x 0.09÷0.002(1 S.F)=2790

    ReplyDelete
  10. (a) 5837 + 985
    ≈ 6000 + 1000 (1sf)
    = 7000
    (correct 7000)

    (b) 347 - 482 + 650
    ≈ 300 - 500 + 700 (1sf)
    = 500
    (wrong -500)

    (c) 23.92 x 4.801
    ≈ 20 x 5 (1sf)
    = 100
    (wrong 1200)

    (e) 62.47 x 0.093 ÷ 0.00217
    ≈ 60 x 0.09 ÷ 0.002 (1sf)
    = 27000
    (wrong 40000)

    ReplyDelete
  11. (a) 5837 + 985 ≈ 7000

    It is reasonable. It is rounded off to 1 significant figure before it is worked out.

    5837 + 985
    ≈ 6000 + 1000 (1 S.F.)
    = 7000

    (b) 347 - 482 + 650 ≈ -500

    No, it is not reasonable. The answer should be 500 instead of -500 as the numbers are rounded to 2 significant figures.

    347 - 482 + 650
    ≈ 350 - 500 + 650 (2 S.F.)
    = -150 + 650
    = 500

    (c) 23.92 x 4.801 ≈ 1200

    No, it is not reasonable. There is an extra 0 in the answer.

    23.92 x 4.801
    ≈ 24 x 5.0 (2 S.F.)
    = 120

    (d) 62.47 x 0.093 ÷ 0.00217 ≈ 40000

    No, it is not reasonable. The answer is too large.

    62.47 x 0.093 ÷ 0.00217
    ≈ 60 x 0.09 ÷ 0.002 (1 S.F.)
    = 2700

    ReplyDelete
  12. 5837 + 985≈ 6000 + 1000 (1sf)
    =7000
    This answer is perfectly correct as the estimation has been done correctly and answering has been done correctly.

    347 - 482 + 650≈ 300 - 500 + 700(1sf)
    =-200 + 700
    = 500
    The first answer was wrong as there is not supposed to be a negative sign in the last answer. This is what the working and answer should be like.

    23.92 x 4.801≈ 24 x 5(1sf)
    = 120
    There is a extra 0 at the end of the answer in the evaluation given. This is how it should be done.

    62.47 x 0.093 ÷ 0.00217≈ 60 x 0.09 ÷ 0.002
    = 5.4 ÷ 0.002
    = 2700
    The first answer given had only been rounded off after the evaluation. This is the correct one.

    ReplyDelete
  13. (a) 5837 + 985 ≈ 7000

    5837 + 985 ≈ 6000 + 1000 (1 S.F)
    = 7000

    The estimation is correct as it had been rounded off correctly, and there were no calculation errors, and the symbols are done correctly.
    (b) 347 - 482 + 650 ≈ -500

    347 - 482 + 650 ≈ 300 - 500 + 700 (1 S.F.)
    = -200 + 700
    = 500

    The estimation is correct as it had been rounded off correctly, but the final answer is wrong. Negative - Positive, and negative is lesser than positive, we should follow the positive sign, so the correct answer should be 500 and not -500.

    (c) 23.92 x 4.801 ≈ 1200

    23.92 x 4.801 ≈ 20 x 5 (1 S.F)
    = 100

    the estimation is wrong. To get a final answer as 1200, the number has to be about 35 x 35. But here, when we round off, it goes to 20 and 5. There is a lot of difference so the answer is obviously not correct.

    (e) 62.47 x 0.093 ÷ 0.00217 ≈ 40000

    62.47 x 0.093 ÷ 0.00217 ≈ 60 x 0.09 ÷ 0.002 (1 S.F)
    = 5.4 ÷ 0.002
    = 2700

    The answer most probably had been rounded off wrongly. The answer is so much larger than the original estimated answer.

    ReplyDelete
  14. (a) is correct.
    (b) is wrong as 300-500+700 (1 S.F.)= 500, which is positive and not negative.
    (c) is wrong as there is an extra zero.
    (d) is wrong as 62x0.09÷0.002=2790
    ≈2700

    ReplyDelete
  15. (a) 5837 + 985 ≈ 7000

    5837 + 985(1SF)
    ≈6000 + 1000
    =7000

    (b) 347 - 482 + 650 ≈ -500

    347 - 482 + 650(1SF)
    ≈300 - 500 + 650
    =450

    (c) 23.92 x 4.801 ≈ 1200

    23.92 x 4.801(1SF)
    ≈20 x 5
    =100

    (e) 62.47 x 0.093 ÷ 0.00217 ≈ 40000

    62.47 x 0.093 ÷ 0.00217(1SF)
    ≈60 x 0.09 ÷ 0.002
    =2700

    ReplyDelete
  16. (a) 5837 + 985 ≈ 7000(1.S.F) Is reasonable

    (b)347 - 482 + 650 ≈ -500 is not resonable, it should be:
    347 - 482 + 650 ≈ 300-500+700(1.S.F)
    = 500

    (c)23.92 x 4.801 ≈ 1200 is not reasonable, it should be:
    23.92 x 4.801 ≈ 20 x 5(1.S.F)
    = 100

    (e) 62.47 x 0.093 ÷ 0.00217 ≈ 40000 is not reasonable, it should be:
    62.47 x 0.093 ÷ 0.00217 ≈ 60 x 0.9÷ 0.002(1.S.F)
    =2700

    ReplyDelete
  17. (a) Is reasonable

    (b) (wrong)347 - 482 + 650
    ≈ 300 - 500 + 700 (1S.F)
    =100

    (c) (wrong)23.92 x 4.801
    ≈ 20 x 5
    = 100

    (e) (wrong) 2.47 x 0.093 ÷ 0.00217
    ≈ 60 x 0.9 ÷ 0.002 (1.S.F)
    =2700

    ReplyDelete
  18. a) Yes.
    5837 + 985 ≈ 6000 + 1000(1SF)
    = 7000

    b) Yes.
    347 - 482 + 650 ≈ 300 - 500 + 700(1SF)
    = 500

    c) No.
    23.92 x 4.801 ≈ 20 x 5(1SF)
    = 100

    e) No.
    62.47 x 0.093 ÷ 0.00217 ≈ 60 x 0.1 ÷ 0.002
    = 6 ÷ 0.002
    = 3000

    ReplyDelete
  19. (a) Yes.
    5837 + 985
    ≈ 6000 + 1000 (1 S.F.)
    = 7000

    (b) Yes.
    347 - 482 + 650
    ≈ 300 - 500 + 700 (1 S.F.)
    = -500

    (c) No.
    23.92 x 4.801
    ≈ 20 * 5 (1 S.F)
    = 100, not 1200

    (e)
    62.47 x 0.093 ÷ 0.00217
    ≈ 60 * 0.09 ÷ 0.002 (1 S.F)
    = 2700, not 40000

    -Christopher Nah
    (Sorry for handing in late!) :(

    ReplyDelete