The recent 2021 PSLE Math paper has done it again! Every year, students and parents take to the internet to consult one another on how to solve a particular math question. This year is no exception.

**Question involved: (source: Mothership and CNA)**

**Question from my whatspp:**

***Apparently, there’s different versions of the question. A reader alerted us.**

I admit. I tried to used algebra to solve it. It didn’t work.

I wanted to text the person who shared the question with me that there must be some other information or that the question is incomplete. Otherwise, how can i not solve it?

My second attempt at the question taught me something. Sometimes, it the user that complicates things. The Singapore Math Model uses Bar Modeling as a pictorial method to solve word problems.

**Solution based on my whatsapp message:**

Please take note that diagram is not drawn to the correct scale. (It doesn’t need to)

And that both Helen and Ivan have the **same** number of coins.

From the above bar model, we can deduce that it does not matter how many coins do each Helen or Ivan has nor does the question ask the student to solve for the total number of coins.

What we should take note of is that as Ivan has **40** more 20 cent coins than Helen, it would mean that Helen would have **40** more 50 cent coins than Ivan. (Only 2 type of coins involved here, 20 cent and 50 cent)

From here, we know that having more 50 cent coins would mean Helen has more money and by $12 (Difference of 50 cent and 20 cent X Difference of 40 coins)

Since Helen has more 50 cent coins, Ivan’s coins would weight lesser than Helen’s. And what’s the difference? (2.7 g X Difference of 40 coins) = 108g difference.

Therefore, mass of Ivan’s coins = 1.134kg – 108g = 1.026kg.

My math tutor used to tell me that it’s alright when I cannot mange to solve certain questions in the paper. I was quite puzzled by what he said. Now, I seem to realize what he meant. He was saying that as his assumption was that I was able to complete the math papers with above 75% grades on a consistent basis. And that if there were any questions that I could not solve, it still would not amount to my grade being less than A1.

However, it has always been my goal to get 100% for my math papers. In reality, when you aim for 100, you may fall short a little (careless mistakes, silly errors, etc). But chances are that you would still get the highest possible grade of A1 or AL1.

So I ask myself: “What would my overall math grade be, if I failed to answer Helen’s and Ivan’s coins question”?

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## Lim Di Vide says:

You forgot to divide the final mass by 2.

## The Learning Space SG says:

Thank you for highlighting! We have updated our post.

So the next question is, who has the correct question? And did the people at CNA and Mothership know about this?

## Ian says:

It is always easier to solve it under no stress, no time limit and on hindsight…and this is just one of the many challenging questions I am sure of the infamous Singapore’s PSLE Maths paper! Imagine what a 12-year old had to go through with on the spot….the tremendous amount of mental stress! So I never bother whether the question is actually solvable, which one does not? It is the amount of stress we are putting on 12-year old at the defining moment.