2013 PSLE Discussions and Strategy

[Jennifer]

zeemimi:

Jennifer:

[quote=\"ngl2010\"]Jen, was the question 3 variables question?

For illustration purpose, I post the qn here. Would you classify this qn as having > 2 variables?

There are some red and blue marbles.
The marbles were packed into 2 containers.
At first, Container A contained 500 marbles and 2/5 of them were blue marbles. Container B contained 300 marbles and 1/5 of them were blue.

Find the total number of red and blue marbles that must be moved from Container A to Container B such that 3/5 of the marbles in Container A are red and 1/4 of the marbles in Container B are blue.

Is the answer 40 Blue and 60 red? Rather tedious. No need algebra. Use ratio. Using 2 variables will complicate everything. Best to express each Blue and red in each container as a fraction of the total number of marbles.[/quote]Yes, your answer is correct :rahrah:

This morning elder boy used ratio to solve but I hv prob understanding his method. Can u pm me how u solve or show the working here? Many thanks in advance.

Almost forgot to ask: would this type of qn appear in PSLE Maths paper?

[snowyqueen]

yogaqueen:

Hi there, I have some experience to share with regard to the use of Algebra in PSLE Math.


Firstly, at the beginning of this school year, I spoke to the school teacher. He stated that Algebra is acceptable but that method marks will not be awarded. So, the trick is, get the final answer right and you can the full marks. Or none.

In the middle of the year, feeling that this was not justified, I wrote to MOE on this particular question of using algebra. MOE did not categorically said Algebra is accepted (despite my re-questioning) but emphasized that any method will be awarded method marks as long as they are used correctly.

Strangely enough, weeks after my letter to MOE, my son came home to tell me his teacher (the same one I asked about Algebra) told everyone in class that Algebra is now acceptable as a method in PSLE Math and method marks will be awarded as long as they are sound.

I taught DD to use algebra to solve problem sums because I think it is more efficient than model method and faster. I had this concern and I checked with her H.O.D. Her reply was algebra is acceptable to be used in PSLE. I also asked about guess n check. It is acceptable if you can use it correctly even though there is straight solution. I taught DD in the worst scenario she really cannot figure out the right method to solve, use guess n check appropriately, not necessary applicable for all, only specific type of questions.

[ngl2010]

yogaqueen:

Hi there, I have some experience to share with regard to the use of Algebra in PSLE Math.


Firstly, at the beginning of this school year, I spoke to the school teacher. He stated that Algebra is acceptable but that method marks will not be awarded. So, the trick is, get the final answer right and you can the full marks. Or none.

In the middle of the year, feeling that this was not justified, I wrote to MOE on this particular question of using algebra. MOE did not categorically said Algebra is accepted (despite my re-questioning) but emphasized that any method will be awarded method marks as long as they are used correctly.

Strangely enough, weeks after my letter to MOE, my son came home to tell me his teacher (the same one I asked about Algebra) told everyone in class that Algebra is now acceptable as a method in PSLE Math and method marks will be awarded as long as they are sound.

So, I guess, bottomline is: don't worry that you will get zero marks if you don't get the final answer correct when using Algebra. You will get some marks for method.e.g stating the correct equations etc.

Thank you, yogaqueen.
:thankyou:

[ngl2010]

For Math’s Pattern problem, is it ok to count manually instead of using formula? This is assuming that the numbers are still reasonable.

[JohnYeo]

ngl2010:

For Math's Pattern problem, is it ok to count manually instead of using formula? This is assuming that the numbers are still reasonable.

what do u mean by reasonable?
Normally the first part still is n the second part is not.

[zeemimi]

Jennifer:

zeemimi:

[quote=\"Jennifer\"]
For illustration purpose, I post the qn here. Would you classify this qn as having > 2 variables?

There are some red and blue marbles.
The marbles were packed into 2 containers.
At first, Container A contained 500 marbles and 2/5 of them were blue marbles. Container B contained 300 marbles and 1/5 of them were blue.

Find the total number of red and blue marbles that must be moved from Container A to Container B such that 3/5 of the marbles in Container A are red and 1/4 of the marbles in Container B are blue.

Is the answer 40 Blue and 60 red? Rather tedious. No need algebra. Use ratio. Using 2 variables will complicate everything. Best to express each Blue and red in each container as a fraction of the total number of marbles.

Yes, your answer is correct :rahrah:

This morning elder boy used ratio to solve but I hv prob understanding his method. Can u pm me how u solve or show the working here? Many thanks in advance.

Almost forgot to ask: would this type of qn appear in PSLE Maths paper? [/quote]A: Blue-200 (200/800 = 10/40)
Red-300 (300/800 = 15/40)
B: Blue-60 (60/800 = 3/40)
Red-240 (240/800 = 12/40)
10+15+3+12= 40 parts
In order to keep the ratio of AB (2): AR (3) , one possible way is to move 2 parts of blue and 3 parts of red. This will result in 5 parts of BB And 15 parts of BR. Hence BB (1) : BR (3)
800 ÷ 40 × 2 = 40
800 ÷ 40 × 3 = 60

[ngl2010]

JohnYeo:

ngl2010:

For Math's Pattern problem, is it ok to count manually instead of using formula? This is assuming that the numbers are still reasonable.

what do u mean by reasonable?
Normally the first part still is n the second part is not.

For example is this question. It is faster to construct a table and write down the number of dots required for Figure 5, 6, 7, and so on rather than to find a formula to calculate which figure will need 108 dots to build. Do you think it is ok to construct a table instead of using a formula to calculate?
http://i40.tinypic.com/4iij4p.jpg\">

[Jennifer]

zeemimi:

Jennifer:

This morning elder boy used ratio to solve but I hv prob understanding his method. Can u pm me how u solve or show the working here? Many thanks in advance.


Almost forgot to ask: would this type of qn appear in PSLE Maths paper?

A: Blue-200 (200/800 = 10/40)
Red-300 (300/800 = 15/40)
B: Blue-60 (60/800 = 3/40)
Red-240 (240/800 = 12/40)
10+15+3+12= 40 parts
In order to keep the ratio of AB (2): AR (3) , one possible way is to move 2 parts of blue and 3 parts of red. This will result in 5 parts of BB And 15 parts of BR. Hence BB (1) : BR (3)
800 ÷ 40 × 2 = 40
800 ÷ 40 × 3 = 60

:thankyou: :udawoman:

[JohnYeo]

ngl2010:

JohnYeo:

[quote=\"ngl2010\"]For Math's Pattern problem, is it ok to count manually instead of using formula? This is assuming that the numbers are still reasonable.

what do u mean by reasonable?
Normally the first part still is n the second part is not.

For example is this question. It is faster to construct a table and write down the number of dots required for Figure 5, 6, 7, and so on rather than to find a formula to calculate which figure will need 108 dots to build. Do you think it is ok to construct a table instead of using a formula to calculate?
http://i40.tinypic.com/4iij4p.jpg\">[/quote]
hmmm...I feel even if we use a table, still need to have a feel what the pattern / formula is in order to solve it. So table is just a way to present or is part of the process of formulating the formula...

[zeemimi]

Jennifer:

zeemimi:

[quote=\"Jennifer\"]Almost forgot to ask: would this type of qn appear in PSLE Maths paper?

There are some red and blue marbles.
The marbles were packed into 2 containers.
At first, Container A contained 500 marbles and 2/5 of them were blue marbles. Container B contained 300 marbles and 1/5 of them were blue.

Find the total number of red and blue marbles that must be moved from Container A to Container B such that 3/5 of the marbles in Container A are red and 1/4 of the marbles in Container B are blue.

A:
Blue-200 (200/800 = 10/40)
Red-300 (300/800 = 15/40)

B:
Blue-60 (60/800 = 3/40)
Red-240 (240/800 = 12/40)

10+15+3+12= 40 parts

In order to keep the ratio of AB (2): AR (3) , one possible way is to move 2 parts of blue and 3 parts of red. This will result in 5 parts of BB And 15 parts of BR. Hence BB (1) : BR (3)

800 ÷ 40 × 2 = 40
800 ÷ 40 × 3 = 60

:thankyou: [/quote]Sorry missed out the last question. This kind of question is possible in psle. Judging from the working, it is characteristic of 5 marks question.

As you can see, the working makes everything look simple. It is the thinking process that is difficult and this question is playing on the children's familiarity with 2 variables questions. But if you use 2 variables, it will complicate everything. My first try was using 2 variables - i gave up after a few steps. So was DS's first try.

The rule in math problem sums is, if after 4 or 5 steps, things get more complicated, abandon it, think simple and redo. It is not that difficult. Evidence: look at all the answer sheets. Hardly any problem sums require more than 6 or 7 steps to get the answer.

Hope this is helpful for those fearful of problem sums.