Q&A - PSLE Math

[tianzhu]

Emelyn:

Tianzhu,


I took another look at your solution.

Why do Ali and Billy have the same number of cards ?
It is not mentioned in the question.

Hi Emelyn

No, Ali had 196, and Billy had 140.They do not have the same number of cards.

If Billy had given 28 cards to Ali,he would have 112 and Ali's new number of cards would be 224, which was twice as many.

The second scenario, Billy and Caven would have 224 cards each if the exchanges had taken place.

Are my answers same as those given in your DS's worksheet?If you play around with the numbers, they look logical.

[Emelyn]

I mean in the model, you drew Ali and Billy having the same number of cards.


I don't understand why.

Maybe I am really slow..... :?

[caroline3sg]

Emelyn

Ali & Billy is not having the same. On top, there is arrow showing Ali 360 and below arrow showing Billy 240.

The orange shaded part being the same is they sold the same number of cards.

[Emelyn]

Hi Caroline3sg,


you are looking at the wrong picture.
It is not the one with the lighthouse on the background. 8-)

It is the last post on Page 15.

[caroline3sg]

emelyn

okay.

For B, it is shaded + 28, originally.

To show comparison of A being 2 times of B, you have to look at after giving. So after giving, it is same line.

[tianzhu]

Emelyn:

I mean in the model, you drew Ali and Billy having the same number of cards.

Hi Emelyn

This is quite an interesting question; have yet to come across one from past years papers.The more common type involves transfers between two parties.

The first scenario is Billy giving to Ali.
Ali has 196 cards and Billy has 140 cards. If Billy gives 28 cards to Ali, he will have 112 cards and Ali, 224 cards. Therefore, Ali has twice as much as Billy.

The second scenario is Caven giving 84 cards to Billy. Caven has 308 cards at first (196+112).Billy has 140 cards. After receiving 84 cards from Caven, he’ll have 224 cards. After giving away 84 cards, Caven will have 224 cards, which is equal to that of Billy.

I think you are wondering why Billy’s 224 cards(after receiving 84 cards from Caven) is equal to that of Ali (after receiving 28 from Billy).This refers to the after events of two different scenarios.This is also the important first step to the solution,where you get your one unit equals to 112 ( 84+28 )

Hope it’s of some help to you.

[Priskhipo]

Emelyn:

I mean in the model, you drew Ali and Billy having the same number of cards.


I don't understand why.

Maybe I am really slow..... :?

Hi Emelyn,
You can draw a smaller unit excluding 28 too. See if you can understand my MD better.

http://www.postimage.org/image.php?v=gx22GUy0

[small]

Thank you for your time.


Question:

Elynn, Fiona and Greg had a total of 336 cards. First Elynn gave Fiona as many cards as Fiona had. Then Fiona gave Greg as many cards as Greg had, and finally Greg gave Elynn as many cards as Elynn had left. In the end, all of them had the same number of cards. How many cards did Elynn have at first? :? :?

[small]

small:

Thank you for your time.


Question:

Elynn, Fiona and Greg had a total of 336 cards. First Elynn gave Fiona as many cards as Fiona had. Then Fiona gave Greg as many cards as Greg had, and finally Greg gave Elynn as many cards as Elynn had left. In the end, all of them had the same number of cards. How many cards did Elynn have at first? :? :?

Not sure whether this is correct or not, base on my working (model method), Elynn had 154 cards at first.

http://www.postimage.org/Pq1ZN9hr

[ksmama]

Hi small, I used different method: work backwards. The answer is 154 like yours.