## Q&A - P3 Math

ChiefKiasu
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### Q&A - P3 Math

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From Ai Tong Pri 3 SA1 Maths:

A teacher gave her students some balloons. If she gave 6 balloons to each student, she will have 2 balloons left. If she gave 8 balloons to each student, she will be short of 2 balloons. What is the smallest possible number of students she has?

Try to do this without using ALGEBRA!
Last edited by ChiefKiasu on Fri Aug 21, 2009 7:49 am, edited 4 times in total.

jedamum
Councillor
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### Re: Try to do this question WITHOUT algebra

ChiefKiasu wrote:From Ai Tong Pri 3 SA1 Maths:

A teacher gave her students some balloons. If she gave 6 balloons to each student, she will have 2 balloons left. If she gave 8 balloons to each student, she will be short of 2 balloons. What is the smallest possible number of students she has?
I'll probably use trial and error method and hope that she is not giving out >100 balloons.
Ans: 2 students...correct?

ChiefKiasu
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### Re: Try to do this question WITHOUT algebra

jedamum wrote: I'll probably use trial and error method and hope that she is not giving out >100 balloons.
Ans: 2 students...correct?
That's what we will get when we use algebra, ie. solve for:
6x + 2 = 8x - 2
=> 2x = 4
=> x = 2

Just that the case in question is given the answer of 14 in "illegal" black-market exam papers. Shows how bad the answers can be! So don't trust the answers provided.

Also, it is difficult with people not trained to do modelling to work out this problem without algebra.

jedamum
Councillor
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### Re: Try to do this question WITHOUT algebra

ChiefKiasu wrote:
jedamum wrote: I'll probably use trial and error method and hope that she is not giving out >100 balloons.
Ans: 2 students...correct?
That's what we will get when we use algebra, ie. solve for:
6x + 2 = 8x - 2
=> 2x = 4
=> x = 2

Just that the case in question is given the answer of 14 in "illegal" black-market exam papers. Shows how bad the answers can be! So don't trust the answers provided.

Also, it is difficult with people not trained to do modelling to work out this problem without algebra.
illegal black-market exams papers aside, nowadays assessment books in the market also have typo, questions and answers error!

lizawa
BrownBelt
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For P3, I expect this question to test on multiplication / division + process skills.

Multiples of 6 : 6, 12, 18,24, ...
+2 (since 2 balloons left) : 8, 14, 20, 26...

Multiples of 8 : 8, 16, 24, 32, ...
-2 (short of 2 ballons) : 6, 14, 22, 30....

Since asking for smallest number of students, the number that match in both cases is 14, hence, number of students is 2.

Liz

ChiefKiasu
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lizawa wrote:For P3, I expect this question to test on multiplication / division + process skills.

Multiples of 6 : 6, 12, 18,24, ...
+2 (since 2 balloons left) : 8, 14, 20, 26...

Multiples of 8 : 8, 16, 24, 32, ...
-2 (short of 2 ballons) : 6, 14, 22, 30....

Since asking for smallest number of students, the number that match in both cases is 14, hence, number of students is 2.

Liz
OK... Liz is the one with the right answer and methodology. All of us are "old school". Back to school, everyone.

lizawa
BrownBelt
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Yeah, when you have to coach your own children from P1 - P6 with all the new-aged methods and syllabus, the only way is to unlearn and relearn.

Liz

phantom
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Talking about unlearn, where can I get information on those new methods?

lizawa
BrownBelt
Posts: 665
Joined: Tue Apr 22,
I follow through my children's text books and look at some of the guide books. Take a while to get used to. The modelling method that they use for Primary Mathematics is very visual. So your child needs to be able to visualize in order to draw the model and solve the problem. It's just another way of solving problems.

Liz

phantom