Q&A - PSLE Math

[tianzhu]

Happy Mama:

Oh ok. Thank you very much, Tianzhu.

Hi Happy Mama

You're welcome.

Best wishes

[Emelyn]

tianzhu:

Emelyn:

Hi,


Need some urgent help here.

Qn : Jan and Kay had equal number of sweets and equal number of chocolates. Jan ate 12 sweets and Kay ate 18 chocolates and then the ratio of Jan's sweets to chocolates became 1:7, and the ration of Kay's sweets to chocolates became 1:4. How many sweets did Jan have at first ?

MTIA !!

Hi Emelyn

This question has been discussed earlier.

This question is a modified version of a question from PSLE 2009.

You may use MD or Units Method to solve it.

Once you get the MD done, all you need to do is to compare the number of chocolates of Jan and Kay.

Hope this helps.

Best wishes.

Oopss... sorry.... for not checking the earlier discussion.
Thanks for explaining it again.

[is_me_lblue]

Hi,


Is m again.

5 sharpeners and 8 books cost $ 49. If 1 sharpener and 1 book cost $u, Find the cost if 9 books.


Thank you.

[Belle2011]

is_me_lblue:

Hi,


Is m again.

5 sharpeners and 8 books cost $ 49. If 1 sharpener and 1 book cost $u, Find the cost if 9 books.

Thank you.

I can't think of any method except \"algebra\" method.

5s + 8b = 49
Since 1s + 1b = u, so 5s + 5b = 5u.
Subtracting:
3b = 49-5u
9 books = 9b = 3(49-5u).

[is_me_lblue]

Belle2011:

is_me_lblue:

Hi,


Is m again.

5 sharpeners and 8 books cost $ 49. If 1 sharpener and 1 book cost $u, Find the cost if 9 books.

Thank you.

I can't think of any method except \"algebra\" method.

5s + 8b = 49
Since 1s + 1b = u, so 5s + 5b = 5u.
Subtracting:
3b = 49-5u
9 books = 9b = 3(49-5u).

Thank you. Same as me but the answer sheet given is $(147-15u).I want to confirm is the answer sheet wrong or ?

[Belle2011]

is_me_lblue:

Thank you. Same as me but the answer sheet given is $(147-15u).I want to confirm is the answer sheet wrong or ?

147-15u = 3(49-5u) !!!

[is_me_lblue]

Belle2011:

is_me_lblue:

Thank you. Same as me but the answer sheet given is $(147-15u).I want to confirm is the answer sheet wrong or ?

147-15u = 3(49-5u) !!!

Oh gosh, :roll: , thank you

[tianzhu]

Hi Belle2011


Good Morning.

In this question, we use a strategy called “Working Backwards”.

We need to recognize that the two fractions are of different measures --- fraction of a tin of cookies and fraction of a single piece of cookie.

Before I begin, I want to emphasise that you may also do this question without MD if you are able to visualise the flow of events without the help of a picture.

I’ve included MD in my solution as it’ll help students to see the transactions.

I’ll try to break down the solution into four steps to show the flow of events, hope it’s useful to you.

After B took 5/6 of the remaining tin of cookies, 1/6 of the tin was left. This 1/6 of tin comprises of 1/3 of a cookie and the remaining 2 cookies, therefore 1 unit equals 2 1/3.

Once you become more familiar with this strategy, you may consolidate into one MD as shown in my earlier solution.

Best wishes

http://farm6.static.flickr.com/5211/5487752786_819943e736_b.jpg\">

[Belle2011]

tianzhu:

Hi Belle2011


Good Morning.

In this question, we use a strategy called “Working Backwards”.

We need to recognize that the fractions are of different measures --- fraction of a tin of cookies and fraction of a single piece of cookie.

Before I begin, I want to emphasise that you may also do this question without MD if are able to visualise the flow of events without the help of a picture.

I’ve included MD in my solution as it’ll help students to see the transactions.

I’ll try to break down the solution into four steps to show the flow of events, hope it’s useful to you.

After B took 5/6 of the remaining tin of cookies, 1/6 of the tin was left. This 1/6 of tin comprises of 1/3 of a cookie and the remaining 2 cookies, therefore 1 unit equals 2 1/3.

Once you become more familiar with this strategy, you may consolidate into one MD as shown in my earlier solution.

Best wishes

http://farm6.static.flickr.com/5211/5487752786_819943e736_b.jpg\">

Dear tian-zhu,
Thank very much for sharing another way of presenting the solution.
I was stuck with \"After B took 5/6 of the remaining tin of cookies...\".
So 5/6 * 1/6 = 5/36.
I am thinking \"my gosh! 5/36, how to draw the model...\".
Anyway, I am trying to reduce the number of 5 mark problem sums which I can't solve to as low as possible and you have been helping me all along.
Once again, thanks a lot.
Cheers,
Belle.

[tisha]

Need help with this question:


Susan takes 2 hrs to travel from Town A to Town B. Helen takes 3 hrs to travel from Town B to Town A. How long will it take for both Susan and Helen to meet along the way?