**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*

5837+985≈7000 is reasonable as the numbers were rounded correctly and evaluated correctly.

ReplyDelete347-482+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

a) Yes.

ReplyDelete5837 + 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

(a) 5837 + 985 ≈ 7000

ReplyDeleteThis 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

a) It is reasonable. 6000 + 1000 ≠ 7000

ReplyDeleteb)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

a) It is definitely reasonable as the answer is correct

ReplyDelete5837 + 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

This comment has been removed by the author.

ReplyDelete(a)Yes

ReplyDelete5837+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

(a) Definitely yes!

ReplyDelete5837 + 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

(a) 5837 + 985 ≈ 7000

ReplyDeleteYes 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

(a) 5837 + 985

ReplyDelete≈ 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)

(a) 5837 + 985 ≈ 7000

ReplyDeleteIt 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

5837 + 985≈ 6000 + 1000 (1sf)

ReplyDelete=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.

(a) 5837 + 985 ≈ 7000

ReplyDelete5837 + 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.

(a) is correct.

ReplyDelete(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

(a) 5837 + 985 ≈ 7000

ReplyDelete5837 + 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

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

ReplyDelete(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

(a) Is reasonable

ReplyDelete(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

a) Yes.

ReplyDelete5837 + 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

(a) Yes.

ReplyDelete5837 + 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!) :(