PSLE - New Format for Maths

[Mandy-Alex]

Guan Hui:

John inherited $25,000 and invested part of it in a money market account, part in municipal bonds, and part in a mutual fund. After one year, he received a total of $1,620 in simple interest from the three investments. The money market paid 6% annually, the bonds paid 7% annually, and the mutually fund paid 8% annually. There was $6,000 more invested in the bonds than the mutual funds. Find the amount John invested in each category


Money invest model
MM [ ] |
MB [1u ][6000] }$25000
MF [ 1u] |

25000-6000=$19000
MM= 19000-2u

Interest received for the $6000 invested in municipal bonds
7% x 6000=7/100 x 6000
=7 x 60
=$420

$1620- $420= $1200

interest receive from 19000-2u of MM
6% x (19000-2u)=19000x 6% -2u x 6%
=(114000-12u)/100
interest receive from 1 u of MB
7% x 1u= 7u/100
interest receive from 1 u of MF
8% x 1u= 8u/100

$1200=120000/100

since all is divided by 100 we can ignore them(multiply all by 100)

114000-12u+7u+8u=120000
3u +114000=120000
3u=6000
1u=$2000

money invested in MM
19000-2u=19000-2x2000
=19000- 4000
=$15000
money invested in MB
1u+6000=2000+6000
=$8000
money invested in MF
1u=$2000

double check
15000 X 6%= $900
8000 X 7%= $560
2000X 8%= $160
900+560+160=$1620(correct)

hope this helps=D But still seems algebra to me :stupid:

Hi Guan Hui,

I think algebra method will look more like that!
Three equations and that's all!


F+6000=B (1) --->> F=B-6000
6M+7B+8F=162000 (2)
M+B+F=25000 (3) --->>M+B+(B-6000)=25000 -->>M=31000-2B


If we put for F=B-6000 and for M=31000-2B in the second equation and after few calculation we will get that B=$8000,

Than F=B-6000=8000-6000 F=$2000,

For M=31000-2B=31000-16000 M=$15000



The last will be 7%x $8000=$560

8%x $2000=$160

9%x $15000=$900

It seems easier than any model.




Regards :lol:

[Guan Hui]

I can solve it in with 1 equation straight. Just trying to make the model make sense... but the space are canceled so the model looks wierd...=((

trying my answer more understandable thats all
Think next time I'll just use photoshop to make a jpeg and paste it here :lol:
I know algebra is surely more easy.. but enoawng say:Can anyone help me to solve this below using the model method? thats y the model method

[Mandy-Alex]

Guan Hui:

I can solve it in with 1 equation straight. Just trying to make the model make sense... but the space are canceled so the model looks wierd...=((

trying my answer more understandable thats all
Think next time I'll just use photoshop to make a jpeg and paste it here :lol:
I know algebra is surely more easy.. but enoawng say:Can anyone help me to solve this below using the model method? thats y the model method

OK! I just sow his/her request! Previously I did not go up to the beginning!

[Guan Hui]

Hehe=) np :lol:

Glad that the PSLE is officially finally over. Parents of P6 students and P6 students you all deserve A GOOD REST!! Enjoy the rest of the year^^ CHEERS!

[lambchop1976]

Dear Parents of current P6 and those who posted their views,


I salute all of you for your various contributions and I really read with much interest. Well I am not a parent who kids are any near to P6. They aint even in p1 yet. H/w as ex-tchr, I really very interested in what going on at primary sch lvl.

As i read all the posts with interest esp those that states the PSLE Maths qns. I must say they are tough. And pls say to your little ones :\" Aunt here salute them too for being courageous to even sit thro the pp. Mayb if i m to sit fr the pp, i may cry so tough!!

It does not matter whether current P6 or p5 or p4 ...parents to prepare your kids for tough sums/PSLE .. do tons of assessmt bks, ttn ctrs etc...
But hv u all wonder is it necessary for the questions to be so tough in the first place? Wat r the examiners trying to prove? That they are clever and the stdnts are stupid??

Whn i was a tchr (ws tchg in TOP sec school wher stdnts are top 5%), i always wonder why some of these TOP stdnts aint so TOP whn they r in sec. They seems to show a sharp decline in their ability may it be maths or science. I rmb my ex-colleague who commented a Sec2 gal(T-score 269) did a chinese compo test n her std ws at most p4 ...why?

I mean lets be honest how many of us can really do those many tough qns in that ltd time and under the envt and conditions. Pressure cooker u know. :stupid: Whn i saw those qns i feel so stupid.

Heard some excuses MOE gave was that the stdnts hv calculators to aid them. Oh pls...qns like the sweets Jim or Joe or watevr have and Ken with sweets (ratio qns) if u cant grasp the concept/understd, the calculator is just a white elephant.

No wonder Maths kills some many brain cells and thus kids these days hate it! :?:

[mum42]

Hi i am a new mum joining this forum. Can someone help me solve this PSLE Question? Do not know the actual question but is something like : 6 pupils rented 4 computers for 2.5hrs each how long can each of them play equally? Son ans is 100mins but friend's daughter got 50mins and insisted is the correct ans. :?:

[Mandy-Alex]

mum42:

Hi i am a new mum joining this forum. Can someone help me solve this PSLE Question? Do not know the actual question but is something like : 6 pupils rented 4 computers for 2.5hrs each how long can each of them play equally? Son ans is 100mins but friend's daughter got 50mins and insisted is the correct ans. :?:

Hi Mum42,
Welcome!
For this Q, my solving is a bit different from that I saw here, in the forum. Anyway I think it's correct and my ans is 100.


The solving:

6 pupils ---> 4 computers --->2h 30 min (150 min),

Let say the pupils are 4, than

4 pupils ---> 4 computers ---> 150 min, here is clear. Every pupil will use a computer for 150 min, but the pupils are 6.

Than 150 min x 4 computers = 600 min

600 min:6 pupils=100 min for every one of the pupils.


Your son ans is correct!
:lol:
But I can't say the same for my daughter's ans

[enoawng]

Guan Hui:

I can solve it in with 1 equation straight. Just trying to make the model make sense... but the space are canceled so the model looks wierd...=((

trying my answer more understandable thats all
Think next time I'll just use photoshop to make a jpeg and paste it here :lol:
I know algebra is surely more easy.. but enoawng say:Can anyone help me to solve this below using the model method? thats y the model method

Thanks everyone. My view is that algebra is more suited for complex problems and in particular its ability to frame complex problems so that we can understand it and solve it step by step.

I am bewildered and annoyed why forumers insist that combination of models/heuristic & partial algebra is the more powerful method to solve complex problems.

However I do acknowledge that using simple models teaches our kids think differently when approaching a problem.

Nevertheless I can only speculate that those who insists on model being the best method for complex problems have self interest in mind to further the intake of students for maths tuition.

Like to hear the views of others.

[atutor2001]

enoawng:

atutor2001:

Fully agreed. However, please don't condemn \"model\" completely to the dungeon. It is a very powerful tool for solving question with minimum information.

Models are useful to solve problems up to a point of complexity.

Beyond that point, models are useless because the human mind can only handle a limited amount of complexity at the same time.

Einstein, Newton didn't use models or did they?

I used to share your view until encountering question with minimum information given. Then it dawn on me that using algebra for such problem requires the use of a few unknowns, which will cancelled off at the end. It takes great confidence for a P6 to use so many unknowns and the steps is quite laborious. Below is a sample of the type of question, previous posted in this forum, where the use of model simplified the process to the solution :

Tim walks to school from his home. One day, as he was walking pass a junction, he remembered that he left his wallet at home and he ran back to take his wallet and ran from home to school. He reached school at the same time as he usually did. The ratio of his running speed to his walking speed is 5:2. Given that the distance from the junction to his school is 1km, what is the distance between his home and school?

[enoawng]

[quote]
I used to share your view until encountering question with minimum information given. Then it dawn on me that using algebra for such problem requires the use of a few unknowns, which will cancelled off at the end. It takes great confidence for a P6 to use so many unknowns and the steps is quite laborious. Below is a sample of the type of question, previous posted in this forum, where the use of model simplified the process to the solution :

Tim walks to school from his home. One day, as he was walking pass a junction, he remembered that he left his wallet at home and he ran back to take his wallet and ran from home to school. He reached school at the same time as he usually did. The ratio of his running speed to his walking speed is 5:2. Given that the distance from the junction to his school is 1km, what is the distance between his home and school?[/quote]D/W=(D-1)/W+2(D-1+D)/2(R)
Substitute 2R=5W
D/W=(D-1)/W+(4D-2)/5W
eliminate W
D=D-1+(4D-2)/5
D=7/4 ............
(I'm not sure where is the issue)

My view is that these minimum information problems are specifically designed to promote the use of models meaning if you change the information slightly the model method breaks down, whereas the algebric method is agnostic to the design of the question

Tim walks to school from his home. One day, as he was walking pass a junction, he remembered that he left his wallet at home and he ran back to take his wallet and ran from home to school. He reached school at the same time as he usually did. Tim's running speed is 2km/hr more than his walking speed. Given that the distance from the junction to his school is 1km, express the distance to school in terms of his walking speed?