Q&A - PSLE Math

[rocklee]

Hi Tianzhu


Yesterday, my son came back with a few challenging questions involving the units and parts method. It took me an hour to help solve all of them. These questions could have been solved within minutes using algebra. Unfortunately, kids are not taught using 2 variables. Hence, I have to go figure out what this "units and parts method" is all about. No wonder parents and kids get so stressed up nowadays.

This thread has more than 800 pages. I wonder if you have by chance helped solve the "Double IFs’ type of questions? Is yes, appreciate if you could direct me to those pages.

Million thanks.

[Musicstar]

Thank you Tianzhu. I like your picture below. It is colourful , good illustration and with panda photo which my girl likes it very much.

quote=\"tianzhu\"]

Musicstar:

Can help to explain why 5-4 = 3-2=7 yrs. I still do not understand. is it must make both ratio diff of 1.

Hi

Good Morning

PapayaDad has shown one way of solving your question using UP.Some students may prefer to use it because it gives them a standard way of solving many \"before and after scenario type of questions\".

As for the answer presented in your post, it actually makes use of equivalent ratios taking into consideration that the difference in age between Samuel and George stays the same.

If you compare the units;

7 years ago
Samuel ----- 4u
George ----- 2u

This Year
Samuel ----- 5u
George ----- 3u

You may choose to use the unit for Samuel or George as the difference in their age stays the same (7).

You may use 5 - 4 --- 1 or 3 - 2 --- 1.

There are different ways to present the solution, I've shown one one way.Choose the format your kid is comfortable with.

Hope this helps.

Best wishes

http://farm9.staticflickr.com/8116/8640747153_e7148d4293_z.jpg\">[/quote]

[PapayaDad]

Hi tianzhu,


I learn from your blog too. Thanks a lot.

rocklee,

You may want to check out the blog too :

http://www.kiasuparents.com/kiasu/content/math-questions-involving-two-changed-quantities

[Oldschool]

Musicstar:

Hi oldschool,

Can help to explain why 5-4 = 3-2=7 yrs. I still do not understand. is it must make both ratio diff of 1. Sorry , maybe my english not good cannot understand .

Hi,

Sorry for not been clearer.

To add further,

a) the age difference between Sam and George is always the same no matter how old or young they are.

e.g. If Sam is born in 1990 and George in 2000, their age difference is always 10.

b) the age difference between now (2013) and 7 years ago (2006) is the same for everybody. i.e. 7 years.

Regards

[tianzhu]

rocklee:

Hi Tianzhu


Yesterday, my son came back with a few challenging questions involving the units and parts method. It took me an hour to help solve all of them. These questions could have been solved within minutes using algebra. Unfortunately, kids are not taught using 2 variables. Hence, I have to go figure out what this \"units and parts method\" is all about. No wonder parents and kids get so stressed up nowadays.

This thread has more than 800 pages. I wonder if you have by chance helped solve the \"Double IFs' type of questions? Is yes, appreciate if you could direct me to those pages.

Million thanks.

Hi

Actually, there are two variables in UP, units and parts. Students are dealing with two equations, but it is packaged that in such a way that it looks less frightening to kids.

Before I go on, I must say I am a post PSLE dad, which means I’ve not been reading the latest books or past years papers for the last few years already.

I may not be able to give you examples of the latest trend of exam questions, if any.

Let me search through some slides of the past years questions on two ifs I had done tomorrow afternoon.

I’ll PM to you by Mon afternoon.

Best wishes

[ozora]

Apologies for repeated request

\t
Need some guide for this age question.
When Mrs Sam was 40 years old, her son was twice her daughter’s age.
Mrs Sam would be twice her son’s age when her daughter was 28 years old.
How old would Mrs Sam be when her daughter was 20 years old?
I got the answer of 56 using algebra and using model.
Anymore other alternative?

[MathIzzzFun]

ozora:

Apologies for repeated request

\t
Need some guide for this age question.
When Mrs Sam was 40 years old, her son was twice her daughter's age.
Mrs Sam would be twice her son's age when her daughter was 28 years old.
How old would Mrs Sam be when her daughter was 20 years old?
I got the answer of 56 using algebra and using model.
Anymore other alternative?

Are u looking for any specific approach.... here's a similar question-

http://www.flickr.com/photos/mathizzzfun/5679985631/in/photostream

cheers.

[rocklee]

Thanks PapayaDad for directing me to Tianzhu’s blog. Tianzhu’s blog has been really helpful.


A big thank you to Tianzhu for your time in looking up the slides.

How nice if all these different methods of solving problem sums are included in the textbooks and properly taught by school teachers, then we parents can save the time in sourcing for solutions and teaching kids ourselves!

[Musicstar]

Hi,


Someone can help to explain the answer provided. How to get 1 part of mangoes + 2 parts of durians = 4 x 164? I cannot figure it out.

Questions : Alan had a total of 448 mangoes and durians. He sold 1/4 of the mangoes and 1/2 of the durians. he sold 164 fruits altogether. How many mangoes and durians were sold respectively?

Answer :
1/4 part of mangoes + 1/2 part of durians = 164
1 part of mangoes + 2 parts of durians = 4 x 164 = 656
1 part of mangoes + 1 part of durians = 448
1 part of durians = 656 - 448 = 208
1/2 part of durians = 1/2 x 208 = 104
164-104 = 60
Alan sold 60 mangoes and 104 durians

[PapayaDad]

0.25m + 0.5d = 164

multiply everything by 4
1m+2d=4x164