## Tuesday, 5 March 2013

### Algebra... Different "Faces" of Algebra (I)

The total length of 4 roads is (3x - 1) km.
What are the possible lengths of the 4 roads in kilometres?

e.g. The length of the 4 roads are: x km, x km, x-7 km, 6 km
Check: x + x + (x - 7) + 6 = 3x - 1

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2. x-1, x, 0.5x, 0.5x

1. Forgot the units. Its all in km

2. Correct but there are units missing (km).

3. (x+1)+(x+8)+(x-11)+1
Check x+1+x+8+x-11+1

1. Its correct. But presentation is for checking only. No conclusion

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5. x-5 km, x+5 km, x-10 km, 9 km

6. x km, x/2 km, (x/2-1)km, x km

7. 0.5x,1x,0.5x,1x + (-1)km
check 0.5x+0.5x+1x+(-1)
=(3x-1)km

1. 0.5x+0.5x+1x+1x+(-1)

2. 1X + (-1)km shld be (X-1)km

8. 5,x+7,x-13,x

9. 0.5x, 0.5x, x-1,x

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2. You are right.

3. OH!
You forgot the (km) so you are wrong!

10. x km + x km + x+10 km+ x-9 km

1. Your answer is wrong Jian Qing. x km+x km is 2x km. 2x km + (x+10 km) is 3x +10 km. 3x + (x-9 km) is 4x + 1 km.

11. (X-10000, X-20000 , X+30000 , X-1)

12. the lengths of the 4 roads are : x - 5km, x km, x + 1km, 3km

1. Correct-a-mungo!

13. (x-8)+x+x+7=3x-1

1. correct... but missed out "km" :|

2. and never state separate four lengths

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15. x km + x km + 20km + x - 19km = 3 x -1

1. Correct. But x-19km should be in brackets and answer is missing the units.

16. x-1,2/3x,2/3x,2/3x

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2. You're missing out on your units and the brackets for the fractions.

17. x+1, 0.5x, x-2, 0.5x

18. 0.5x+0.5x+x+x+(-1)=(3x-1)

1. just write x-1...

2. but still correct

19. 0.75x, 0.75x, 0.5x, x-1

1. all okay. Units? km/cm/m/\$/min?

20. 0.5x KM, 0.5x KM, 0.5 x KM, 1.5 x KM -1

check: 0.5x +0.5x +0.5 + 1.5x-1 = 3x-1

1. *** 0.5x

u missed the x in 0.5, so is incorrect

21. x+x+100km+x-99

1. ITS CORRECT

2. But missing units

22. (x+1)+(x+7)+(x-10)+1 (km)

23. 0.5x , 0.5x , 0.5x , 1.5x-1km