Q&A - PSLE Math

[PiggyLalala]

comfy:

I understand the step till extra books bought 20/2.5=8

But can explain the next step? why need to 50-8?

Let me try again.
8 extra books here mean if Mary buys 50 books, then it will be 8 more than the number of books she bought at first.

Hence the number of books that mary bought at first = 50 - 8 = 42.

Sorry i am not very good in explaining how i arrive at my answer. Hope you can understand. Maybe others can help. You can also look at Tianzhu's solution.

[PiggyLalala]

tianzhu:

comfy:

Mary bought a total of 50 books and pens. Each book cost $7.80 and each pen cost $5.30. If she bought 50 books, she had to pay $20 more. How many books and pens did she buy at first?

Hi

Another way to look at it is to rewrite the question in another way.

50*7.8 ------390
390-20 -----370

Now rewrite the question as follows:

Mary bought a total of 50 books and pens. Each book cost $7.80 and each pen cost $5.30. She spent $370. How many books and pens did she buy at first?

Does this look familiar? It’s a common “Make a Supposition” or “Counting heads and legs” type of question.

The answer is 42 books and 8 pens.

Best wishes

Thank you for showing us another way doing this question.
I love your way of transforming a difficult question to one that students are familiar with. I feel that this way of teaching is especially good for the weaker students.

Good luck to all your students in their coming PSLE too. :rahrah:

[tianzhu]

PiggyLalala:

Thank you for showing us another way doing this question.

I love your way of transforming a difficult question to one that students are familiar with. I feel that this way of teaching is especially good for the weaker students.

Good luck to all your students in their coming PSLE too. :rahrah:

Hi

You're welcome.

I think some students may be caught off guard by this question.
It is actually a familiar question with a slight tweak.

The assumption, “Assume all were books” in this particular question is written as a statement in the question.

Students who understand the concepts should be able to see that the additional number of books is equal to the number of pens. The $20 is due to the book costing $2.50 more than the pen.

My students?

I've no students.

I am not a teacher, I am a simple dad of a post PSLE kid.

Best wishes

[PiggyLalala]

tianzhu:

PiggyLalala:

Thank you for showing us another way doing this question.

I love your way of transforming a difficult question to one that students are familiar with. I feel that this way of teaching is especially good for the weaker students.

Good luck to all your students in their coming PSLE too. :rahrah:

Hi

You're welcome.

I think some students may be caught off guard by this question.
It is actually a familiar question with a slight tweak.

The assumption, “Assume all were books” in this particular question is written as a statement in the question.

Students who understand the concepts should be able to see that the additional number of books is equal to the number of pens. The $20 is due to the book costing $2.50 more than the pen.

My students?

I've no students.

I am not a teacher, I am a simple dad of a post PSLE kid.

Best wishes

Oh sorry.. I thought I have read from previous posts that you are a tutor. Sorry i could have make a mistake.

[tianzhu]

PiggyLalala:

Oh sorry.. I thought I have read from previous posts that you are a tutor. Sorry i could have make a mistake.

Hi PiggyLalala

No worries, enjoy your holidays.

Best wishes

[SaPan]

need help on below question.


some workers arranged chairs in 18 short rows and 7 long rows.
each long row had 32 more chairs than short rows.
half of the chairs were arranged in long rows while 3/7 of the chairs in short rows.
remaining chairs are stacked in a corner.

How many chairs were arranged in rows?

many thanks in advance.

[tianzhu]

SaPan:

some workers arranged chairs in 18 short rows and 7 long rows.
each long row had 32 more chairs than short rows.
half of the chairs were arranged in long rows while 3/7 of the chairs in short rows.
remaining chairs are stacked in a corner.

How many chairs were arranged in rows?

Hi

Long rows (LR) ------ 7 units (1/2 of 14)
Short rows (SR) ------ 6 units (3/7 0f 14)
Stacked up chairs ------ 1 unit

6 units ------ 18SR
1 unit ------ 3SR

1LR ------ 1SR + 32
7LR ------ 7SR + (7*32) ------7SR + 224

You may use MD to compare
7SR + 224 ------- 18SR + 3SR
14SR ----- 224
1SR ----- 16
\t
1 unit ---- 3SR ----- 48
13 units ----- 13*48 -------- 624

Number of chairs (rows) ------ 624

Best wishes

[dnsy]

Hi. Stuck with a question from hokkien huay kuan 2009 Maths preliminary…


A car and a coach travelled from Town A to town B. The coach left town A at 0648 and it took 5 hours to reach town B. The car started 30 minutes later than the coach and it took 4 hours to reach town B. At what time did the car catch up with the coach?

The answer sheet shows 0918 but there is no working…

Thanks!

[tianzhu]

dnsy:

A car and a coach travelled from Town A to town B. The coach left town A at 0648 and it took 5 hours to reach town B. The car started 30 minutes later than the coach and it took 4 hours to reach town B. At what time did the car catch up with the coach?

Hi

This question was discussed in an earlier post.

Please follow this link.
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&hilit=0648+5h&start=1500

Best wishes

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[cimman]

pixiedust:

I interpreted the problem as 'total value / amount before transfer and after transfer should be the same'. Will update all when the teacher explains the solution.

yes, do let us know. It is hard enough to get a child to solve difficult maths problems without having to contend with the interpretation of the problem statement. With a few more words, they could have made the problem statement more defined and not leave room for interpretations.