#trending: Primary 3 mathematics question with right answer marked wrong stumps Singapore netizens

SINGAPORE — A mathematics question has puzzled some people online, after a seemingly correct attempt at solving a multiplication question was marked wrong. 

Reddit user “Lhxlhx” posted a photograph of the math problem sum on the r/Singapore Reddit forum thread on Tuesday (May 9). 

Try solving this: “Mrs Kim gave 5kg of rice to each family. She gave rice to 8 families. How much rice did she give in total?”

The student, who attempted to solve the question, filled in the blanks and wrote that five times eight equals to 40.

“Lhxlhx” who had seen this on her nephew’s workbook questioned why five times eight was marked wrong, while eight times five — which works out to be 40 as well — was deemed correct by the teacher.

This post stirred up a heated debate on the forum, with Reddit users coming up with different theories on why this could be so. 

One commented: “Nothing wrong… Teacher probably needs coffee or something.”

Another agreed: “Highly likely that teacher was marking in autopilot mode. Too many worksheets already, it sometimes just becomes a blur and you don't really see what you're marking.”

Many Reddit users believed that the question was marked wrongly by mistake, while some have suggested that the teacher was probably just following the school curriculum.

They theorised that the method of solving the mathematical question was following the Primary 3 curriculum, which is the same grade level as the nephew of “Lhxlhx”.

One Reddit user said: “When I first learnt multiplication in Primary 1, my maths teacher emphasised that order matters for multiplication at this level, because at this stage, they want to make sure we understand conceptually what multiplication is."

Another user said: "Simply put, '8 x 5 is 8 groups of 5. 5 x 8 is 5 groups of 8'. In the word question, 8 groups of 5 is correct.” 

However, one other person said that this would not be “self-evident when a kid first starts learning multiplication”.

In some curriculum, teachers might want to “emphasise the concept of multiplication as repeated adding first” and “get the kids to visualise 8 groups of 5 bags of rice, that's 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5.”

Therefore, the emphasis is on the order of multiplication being eight times five, instead of the other way round, despite multiplication being commutative. 

Commutative law in math means that the same result occurs, regardless of the order of the quantities involved. For example: A x B = B x A.

On this point, some online users felt that having labels in the workings is important to avoid confusion.

“If the teacher wants to test and emphasise on whether students really understand what they're doing, then they should have insisted that the students put in the labels. Such as 8 families x 5 kg, with the labels being 'families'.”

A Redditor even found a life lesson from this entire incident: “In all honesty, though... It's a good life lesson... Authority figures are often right because of authority, and no other reason.”

Another said that this was "truly" a Singaporean experience.

Indeed, primary school mathematics questions have repeatedly made news in recent years over their difficulty levels.

A 2021 Primary School Leaving Examination (PSLE) mathematics question flummoxed Singaporeans, revolving around calculating the weight of coins.

Preceding that was the infamous 2015 Math Olympiad question that went viral internationally, for its difficulty over figuring out the birthday of a girl named Cheryl.