### Chap 2: Real Numbers - Spot the Common Mistakes (I)

Revision Exercise 2 (p52 of Textbook) No. 7(a)

1. It should be 48-(-40)=88

2. It should be (-40) and not 40.

3. It should be 48-(-40)
=48+40
=88

4. The correct working should be :
(-16)x(-3)-(-8)x5
=48-(-40)
=88

5. its suppose to be
48+8x5
=88

6. (-16)x(-3)-(-8)x5
=48-(-40)
=48+40
=88
The negative sign for '(-8)' disappeared.

7. (-8)x5= to -40 not 40.
so the equation should be: 48 - (-40) = 88

8. It should be negative 40.
(-16)x(-3)-(-8)x5
=48-(-40)
=88

9. it should be:
(-16)*(-3)-(-8)*5
=48-(-40)
=88
and not:
(-16)*(-3)-(-8)*5
=48-40
=8

10. The second part of the equation. (-8)*5 is equal to (-40). When you remove the brackets the negative and the negative while turn into positive. Thus it becomes 48+40=88

11. (-46) x (-3) - (-8) x 5
=48-(-40)
=48+40
=88

12. The working is wrong.
(-16)x(-3)-(-8)x5
=48-40
=8(Ans)

It should be...
(-16)x(-3)-(-8)x5
=48-(-40)
=88(Ans)

13. For the second number sentence, it should be 48+40 instead of 48-40. Thus, the answer should be 88.

14. (16) x (-3) - (-8) x 5
= 48- (-40)

It is 48 subtract (-8) x 5 and not
48 subtract 8 x 5

-Christopher Nah

15. The equation should be expressed like this:
48-(-40)=88 , and not 48-40=8

16. (-16)x(-3)-(-8)x5
=48 - -40
=88

17. It is wrong as (-8) multiplied by 5 = (-40).Then 48-(-40) as negative and negative equals to 48+40.So the answer is 88.

18. It should be
(-16)x(-3)-(-8)x5
=48+8x5
=48+40
=88

19. it is:

(-16)x(-3)-(-8)x5
=48-(-40)
=88

(-16)x(-3)-(-8)x5
=8
=48-40

20. The answer is wrong as (-8)x5 is -40 so if you subtract 48-(-40)equals 88.

(-16)x(-3)-(-8)x5
=48--40
=48+40
=88

22. (-16)x(-3)-(-8)x5
=48+40
=88(Ans)

23. Class S1-02

Well done... all of you are able to identify what's wrong with the working.

Notice that a few of you put down, as part of your working like
48--40 or 48 - -40

Please remember, when we have 2 signs side by side, they have to be separated by the bracket ().

Cheers!
Ms Loh