Singapore PSLE 2015 Math

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PSLE is “Primary School Leaving Exams” for 11~12 year-old children sitting at the end of 6-year primary education. The result is used as selection criteria to enter the secondary school of choice.

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Hint: Without seeing or feeling the weight of the $1 coin, you still can guess the answer. This is the essence of “Singapore Math” — using “Guesstimation“.

Answer (below):
Try before you scroll down.
If wrong answer, please go back to primary school 🙂
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Answer:

By elimination using ‘guesstimation’ method:
A) 6g too light,
D) 6 kg too heavy.
Left B & C…
C) 600 g > half kg for 8 coins ($1), not possible.

Ans: B = 60 g.

Singapore Math for 11-year-old Kids : Modelling

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Compare below the Singapore Math versus Algebra Method:
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Answer:
Mrs. Lim 68 (son 36, daughter 32)

Algebra Method: Try yourself !
(It involves solving 2 equations of 2 variables.)

My Comments:

There are certain types of problem easier to solve with Modelling (example: this one and the “Monkeys & Coconuts Problem” with Modelling Method); whereas there are some other types difficult to visualize in model, but straight forward with Algebra Method.

Modelling Math is excellent for lower primary kids (Primary 1 to Primary 4), while upper primary (Primary 5 – Primary 6) should be taught Algebra (1-variable to 2-variable equations).

The reason in PISA Test China (Shanghai) kids (PISA World’s #1) beat Singapore kids (PISA World’s #2) in Math is they learn Algebra in upper primary schools (11-12 year-old).

Algebra vs Singapore Math

Who wins?

This comic video illustrates Singapore Math’s Arithmetics Polya-style problem solving process vs Algebra’s mechanical method.

The problem is as follow:
R is 3 times older than S two years ago. From now 2 years later, their total age is 32. How old is R now ?

See my previous blog (search “Monkey”) the Nobel Physicist Paul Dirac’s problem “The Monkeys and Coconuts“, 3 methods are used: 2 adanced modern math (by Sequence, eigenvector & eigenvalue), and the easiest & intuitive method (by Singapore Modelling Math). High-school Algebra method is impossible, if not cumbersome, to solve the Monkey problem !