Q&A - PSLE Math

[CoffeeCat]

PiggyLalala:

It is very difficult to find a teacher who can really teach 'drawing model' skills. I believe that there are certain techniques or steps involved. It is NO point saying understanding the question. I can understand the question, BUT still I CANT draw the RIGHT model for certain questions :frustrated: Why? :?

model drawing, is all about transferring the information given in a problem sum to a diagram called a model for manipulating, sentence-by-sentence, step-by-step.
If I m not wrong, what some teachers did will just to draw the complete \"nice nice\" model out. When I teach, I will draw the model step-by-step, emphasizing to my students how I \"SQUEEZE\" information out from each sentence

[Dharma]

ksi:

Dharma:

If Charles continued driving after reaching the finishing line, he would have covered an additional 45km in the same time that Tony took to finish the race.


Time taken by Charles to drive the additional 45km = 45km/(90km/h) = 0.5 hr
Therefore, Charles finished the race (reached the finishing line) ½ hr earlier than Tony.[9.05 a.m.]

Dharma, did you get the names mixed up? I am confused.. :?

Should it be Tony 45 km ahead if he continued the journey, hence time=0.5hr ahead of Charles.
So Charles finished race at 10:05am?

Sorry for getting the names wrong and thanks for alerting, ksi.


If Tony continued driving after reaching the finishing line, he would have covered an additional 45km in the same time that Charles took to finish the race.
Time taken by Tony drive the additional 45km = 45km/(90km/h) = 0.5 hr
Therefore, Charles finished the race (reached the finishing line) ½ hr later than Tony.[10.05 am]

[PiggyLalala]

CoffeeCat:

PiggyLalala:

It is very difficult to find a teacher who can really teach 'drawing model' skills. I believe that there are certain techniques or steps involved. It is NO point saying understanding the question. I can understand the question, BUT still I CANT draw the RIGHT model for certain questions :frustrated: Why? :?

model drawing, is all about transferring the information given in a problem sum to a diagram called a model for manipulating, sentence-by-sentence, step-by-step.
If I m not wrong, what some teachers did will just to draw the complete \"nice nice\" model out. When I teach, I will draw the model step-by-step, emphasizing to my students how I \"SQUEEZE\" information out from each sentence

.

:thankyou: for your sharing. Yup, we do not need teachers who simply draw the complete \"nice nice\" model out. We need teachers to show how to draw the model step-by-step and also what are the things to look out for in model drawing. I have a feeling that the aim in the model drawing is to make as many the bar of the same size as possible, so that we can compare and deduce the answer. But somehow, I still lack of the skills to solve some questions using model. May I ask where did you learn all the modelling skills? Also usually in a complicated word problem, there are always 3 or 4 information in it. How do we know which information to start with when we draw the model? Does it matter as to which information to start with? I have a feeling that if we start with the wrong one, the model may end up to be very messy and complicated? Please enlighten me. Thank you very much.

[MathIzzzFun]

PiggyLalala:

MathIzzzFun:

[quote=\"PiggyLalala\"]Hi MathIzzzFun,

I have found this question in your MathIzzzFun photostream and have read through the solution.
Sandra had twice as many apples as oranges at first. She removed 4 apples and 3 oranges each time. In the end, there were 18 apples and 1 orange left. How many fruits did Sandra have at first?

In this question, there are 3 key information. How do we know which information to start with when we draw the model? If we have drawn the model based on ' Sarah had twice as many apples as oranges at first', then how should we continue drawing the model to show the other 2 key information and to solve the question?

Can you briefly explain how does one go on to draw the model after reading a complicated word problem? THANk YOU very much.

Hi
I have posted the question and solution here.

http://i54.tinypic.com/2rmr48g.jpg\">

For this question, it is easier to start with the end because we have known defined info - 1 and 18. Then we add the units in the ratio of 4 : 3 for apples and oranges accordingly to the 18 and 1. And then we fill in the final part - doubling orange model to \"equalize\" with the apple model. Finally, compare the models and then solve.

Alternatively, we can also start with the known ratio ie number of apples is twice the number of oranges .

http://i55.tinypic.com/2pt7x4x.jpg\">

Then we remove 3 units from orange model leaving \"1\", and 4 units from apple model - note that I have removed 1 unit from the end of apple model to make it easier to visualize the relation. Again, compare the model and solve.


cheers.

:thankyou: :thankyou: :thankyou:
Really appreciate your effort and patience. So it does not matter which information to start with in drawing the model? What are the crucial steps in drawing model? WHat are the common mistakes people make in their model drawing?

Sorry that i have posed so many questions. One last two questions, where did you learn all the model drawing skills? Also is it possible to categorise the Maths questions according to the 'model type'? That means, if i see this type A question, then I know that I have to use Type A model; Type B question = type B question, etc.

TIA.[/quote]Hi

you are welcome, glad to be of help

The basics of modelling are taught in school, and really there are no secret or short cuts or fixed pattern etc. It all depends on the question.

Modelling is algebra in visual form. And it appears easier because one can see the relations and how answers are obtained. It is really like solving a jigsaw after drawing the models - need to manipulate and move the blocks around so \"see\" the relations.

cheers.

[PiggyLalala]

MathIzzzFun:

Hi

you are welcome, glad to be of help

The basics of modelling are taught in school, and really there are no secret or short cuts or fixed pattern etc. It all depends on the question.

Modelling is algebra in visual form. And it appears easier because one can see the relations and how answers are obtained. It is really like solving a jigsaw after drawing the models - need to manipulate and move the blocks around so \"see\" the relations.

cheers.

Thanks for your generous sharing again. I guess the fact that there is no secret or short cuts or fixed patten in modelling make it very tough for teachers to teach and students to master the modelling skills.

Though modelling is algebra in visual form, the manipulating and moving of block to see the relations proved to be invisible for many. :imcool:

[PiggyLalala]

PiggyLalala:

Saw this infamous PSLE 2009 question on a tuition centre leaflet. Decided to post in here before I throw the leaflet away. :razz:


'Jim bought some chocolates and gave half of it to Ken. Ken bought some sweets and gave half of it to Jim. Jim ate 12 sweets and Ken ate 18 chocolates. The ratio of Jim's sweets to chocolates became 1:7 and the ratio of Ken's sweets to chocolates became 1:4. How many sweets did Ken buy?' Answer: 68 sweets.

http://i56.tinypic.com/25ktnv4.png\">

After learning from all the Maths Experts in this forum, here is first attempt in solving a complicated word problem using model. Hope the model and the solution make sense.

[adanial]

Hi,


I'm a newbie here. Not too sure if anyone can help to solve P6 maths problem sum. shd I be posting the questions here. ?

I'm frustrated that I cant help him out in his revision.

pls help

[Brenda10]

Hi, need help as we have a question that can work out the answer (same with answer key) but not sure how to verify.


SGC 2010 Prelim Q13.

Terry bought a vase which he decides to sell. If he sells thh vase at a discount of 20%, he makes a gain of $150. if he sells it at a 45% discount, he loses $325. How much did Terry pay for this vase?

DD working:

45 - 20 = 25
325 + 150 = 475
475 / 25 = 19

80 x 19 - 150 = $1370
55 x 19 + 325 = $1370

How to use this amount $1370 to verify the above statement that he gain or loses ?

Thank you.

[bobsg01]

P6 math problem. :imdrowning:


Thanks for any help rendered.

http://i52.tinypic.com/2regq39.jpg\">

[VisualTextEducation]

Yes. you can post the Question here. I dont mind solving it for you=)