Thursday, May 3

Help your child score A* for PSLE!

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Tuesday, February 28

The Straits Times: Heuristics: A Thinking Tool for Your Child's PSLE Success

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Friday, February 24

Question posted by Parent

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Thursday, February 16

Parents Workshop March 2012

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Wednesday, November 9

Question from Parent

From: Mr Peter Cheng

Hi Sunny, tried applying UTM but can't solve this. Can you advise, tks

J and P had a sum of money. J gave P 0.4 of her money. P then gave J 1/2 of her money. In the end, J had three times the amt of money that P had. If J gave P $125 more than what P gave J , how much money did J have at first?

Ans: $1250.

Thank you

From desk of Sunny Tan……..


Friday, October 28

Heuristics: Effective Approach to A* in PSLE Maths & Science

Sunday, October 9

Primary 4 – Unit Transfer Method Publication, Chaper 2/ Q8 - From Madam Ser, Parent


From: Madam Ser, Parent

Dear Sir

We refer to the UNIT TRANSFER METHOD Primary 4 book, Chap 2, Q8

Mrs Gan is changing the water in her fish tank.
If she uses a 4-litre pail to fill the tank, 4 litres of water will overflow.
If she uses a 2-litre pail to fill the tank, she will need another 3 more pails of water.
How many litres of water are needed to fill the fish tank.

The answer provided by the book indicates that the fish tank’s capacity is “16 litres”

However, when we work backwards :

Case 1:            If fish tank’s capacity is 16 litres, that means that Mrs Gan used 4 pails of 4 litres each to fill the tank. The amount of water available to Mrs Gan was 20 litres, so, 4 litres would overflow.

Case 2:            If fish tank’s capacity is 16 litres, that means that Mrs Gan used 8 pails of 2 litres each to fill the tank. If the amount of water available to Mrs Gan was 20 litres, so, there would still be an excess of 4 litres

Please clarify.

From desk of Sunny Tan……..

Case 1:            If fish tank’s capacity is 16 litres, that means that Mrs Gan used 4 pails of
4 litres each to fill the tank. The amount of water available to Mrs Gan was 20 litres, so, 4 litres would overflow.
Comment:       Therefore the number of pails used is 5 pails.

Case 2:            If fish tank’s capacity is 16 litres, that means that Mrs Gan used 8 pails of 2 litres each to fill the tank. If the amount of water available to Mrs Gan was 20 litres, so, there would still be an excess of 4 litres

Comment 1:   If she use 8 pails of 2-litre each, she will fill up the tank completely, she
will not need another 3 pails, this assumption is invalid as it contradicts the question.

Comment 2:   If the amount of water available to Mrs Gan was 20 litres, so, there
would still be an excess of 4 litres
This assumption is invalid. Case 1 and Case 2 scenarios are if..and if…, the two events never took place. Therefore we cannot assume that 20 litres of water, that is available in Case 1 is equal to that in Case 2.
                       
 Comment 3:  Number of pails = 5 pails.
                        Total volume = 5x2 =10 litres
                        The capacity is 16 litres
                        Therefore she need extra 6 litres, which is 3 additional pails.

 -----------------------------------------------------------------------------------------------------------------

From: Madam Ser, Parent

Dear Sir
Thank you for your explanation.

The model that we created as below:
 U : No. of 4-litre pails
P : No. of 2-litre pails

Capacity of tank = 4U
4 litres that overflowed = 1 pail = 1U

Therefore, 4U = 16 litres

Check :
2P + 6 litres = 4U = 16 litres
Therefore, P = 5 pails of 2-litre each, resulting in shortage of 6 litres (3 pails of 2-litre each)

Please advise if the above interpretation is correct. Else, please help provide working.

Thank you.


From desk of Sunny Tan……..
I noticed from your model, the U and P is the same.
In fact, this fact can be established in the beginning, that is the number of pails used in both scenarios Case 1 and Case 2 are the same.
Thus, it is unnecessary to introduce P, too many unknown variables may confuse the child.

Let define: 1u = represents the number of pails


2 u = 10
1u = 5 (5 pails)

Either use
case 1: 4u – 4 = 4x5 – 4 =16
case 2: 2u + 6 = 2x5 + 6 =16

Hope this helps.
 

Tuesday, October 4

Question from Raymond


Hi Mr Tan

Please help me with the following problem using UTM and model.


45 pupils in a class. 1/4 of boys and 2/3 of girls wear spectacles. 25 pupils wear spectacles. How many girls wear spectacles/ (answer 22)


Thanks
Raymond

From the Desk of Sunny Tan........