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Number and Algebra

Morning Teachers, these questions were posted on behalf of my sister. please advise on the answers. If possible, I would like teachers to give a few pointers on the rules to take note.

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Connie Lim

Asked 7 years ago

SG
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Primary 5
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Number and Algebra

This is a simple question. I used BODMAS to solve and answer is 04. My girl used the method that was taught in school and answer is 28. However the answer sheet is 12. Any good advice for a absolute correct answer / method?

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52

Vina Lim

I got 28 as well

4 years ago

Belle Gan

24-5+8-3+4
=19+8-3+4
=27-3+4
=24+4
=28
First solve the 2x2
After that go from left to right,which ever come first as + and -will be whoever come first..

4 years ago

Serene Khoo

Done by my P6 boy.

4 years ago

Nandula Hema

P5

4 years ago

Cynthia Tan

I got 28 too.. If qns doesn't have brackets, we shouldn't add in ourselves.

4 years ago

Lin Ling Goh

I got 28 too.. The instructions in the p5 school textbook say so to work from left to right, carry out multiplication and division before addition and subtraction.

4 years ago

Toh Kai Wee Jerry

Answer is 28

4 years ago

Tan Weiqiang

The answer is 28.. You work the multiplication first then for the rest you go from left to right. Order of operations

4 years ago

Tan Weiqiang

Answer sheet is wrong.. Oh dear.. The copywriting not good

4 years ago

Goh Thsu Chuan

Very sure answer is 28.

4 years ago

Tan Weiqiang

Definitely 28. :-)

4 years ago

Pieter Cronje

Absolutly! 28 even from where I reside in Southern Africa!

4 years ago

Tan Weiqiang

Lolz Pieter Cronje you are funny.. š and yes I agree with you.. Math is universal..

4 years ago

DonaldNaomi Innes

28 - 2x2 first then work from left to right

4 years ago

Janet Chan

i got 28

4 years ago

Mary-Anne Rischmueller

Yep I get 28 too, answer sheet must be wrong, glad to have my understanding confirmed by everyone here.

4 years ago

Fiona Ang

i got 12. work out answer for 2x2 first.and 5+8. 24 less 13=11 less 3=8 +4=12.

4 years ago

Janet Chan

i rem when young, my tr taught me using this BODMAS to solve such sum. š

4 years ago

Mary-Anne Rischmueller

Ng, why would you do -5 + 8 ? After multiplying the 2x2, wouldn't you start with 24 -5 ?

4 years ago

Janet Chan

Mary-Anne Rischmueller, i guess ng is trying to tell fiona that in this sum the 5 is a negative 5 instead of a positive 5..

4 years ago

Mary-Anne Rischmueller

Ah ok I see, Fiona adds the 5+ 8, maybe she thinks addition is done before the subtractions. One of the misconceptions of Bodmas

4 years ago

Mary-Anne Rischmueller

That is a new of showing it Ng, thanks

4 years ago

Rezal Samad

just use BODMAS RULE
Bracket
Division
Multiplication
Addition
Subtraction

4 years ago

Mary-Anne Rischmueller

The trouble starts when people think that addition comes before subtraction or when division comes before Multiplication. Addition and subtraction should be bracketed to show they are done in order from left to right. Same with division and multiplication.

4 years ago

Rezal Samad

yes Mary 100% agreed.. They must understand the concept first...

4 years ago

Janet Chan

Rezal Samad, there is still a O in BODMAS..
Bracket
Of
Division
Multiplication
Addition
Subtraction

4 years ago

Rezal Samad

hehehe

4 years ago

Janet Chan

Rezal Samad, we are here to learn from one another. cheerios! š

4 years ago

Fiona Ang

tks for clarification

4 years ago

Tan Weiqiang

You are right Mary-Anne Rischmueller.. That's why I teach my student's the addition and subtraction are BFFs.. So doesn't matter the order.. Just left to right. Same case for multiplication and division.

4 years ago

Tan Weiqiang

Of course.. Multiplication and division must be tended to first

4 years ago

Mary-Anne Rischmueller

You explained it more clearly Tan, thanks

4 years ago

Tan Weiqiang

Thank you Mary. Just sharing what I used while I was teaching and what I used at my centre that worked.. I usually don't use BODMAS.. Cos students can get confused and want to do division before multiplication and addition before subtraction.
I usually use an analogy of queuing up at a stall to start. Brackets are the most senior folks so they go first.. Followed by multiplication and division but they are BFFs so they wouldn't mind who gets tended to first.. So they go from left to right. Finally there's addition and subtraction.. Again they're BFFs so again left to right.
This little story usually works...
Just sharing. :-)

4 years ago

Mary-Anne Rischmueller

Love it, analogies help a lot in teaching. I will use this idea, thanks.

4 years ago

Tan Weiqiang

Cheers Mary.. Hope you'll find this useful

4 years ago

Pieter Cronje

I like your BFFs as well ! Kids luv reminders that they identify with and has an element of humor. If we create a luv for maths we have achieved our goal!

4 years ago

Tan Weiqiang

Thank you Pieter Cronje! Hope it'll work for you too! Cheers

4 years ago

Tan Seng Hoo

My way will be do 2x2 =4, then re-arrange all + sign, then the last sign is - so we take 24+8+4-5-3=28 this method usually for P6 n sec 1 students, again applying BODMAS n to build my strong foundations during PSLE, mine is ALWAYS strong alegrbric during PSLE, n sec 1 n 2 so that this student can do hos A maths in upper secondary no problems at all. The whole textbook is all about x, y, z, alpha, beta and so on so forth. I criticize even today is about solving using model method which will be TOTALLY obsolete in secondary level. Better to build STRONG foundations early
Assuming that question is 24a-5b+8a-3b+2aĆ2c, then this poor student will have NO PROBLEM if he masters this in PSLE.

4 years ago

Tan Weiqiang

Whichever works for you Tan Seng Hoo. Cheers

4 years ago

Mary-Anne Rischmueller

Tan Seng Hoo, probably more mathematically correct but I am a primary school teacher, not a mathematician and I don't understand it totally and I'm sure if I did, the kids would never understand it.

4 years ago

DonaldNaomi Innes

Sorry what is psle?

4 years ago

Tan Seng Hoo

Primary School Leaving Examination. Pupils who are usually 12 years old and attending Primary 6 will sit for this very important exam sometime towards end of September or early October. Results will be known towards end of November. Those who passed the exam will be posted to either 4 or 5 years of secondary education.

4 years ago

Tan Weiqiang

In afraid we're on different pages my friend Mr Tan Seng Hoo. We're on this page cos we are discussing ways to educate for understanding for the purpose of lifelong knowledge. We're not discussing ways to get students to score in national exams. Many of us here use the model method and I have to disagree with you when you said that the model method is going to be obsolete. In a way you are right but in Algebra.. We are looking for the unknown.. The model represents the unknown and students look for the unknown. This is a leadup to more complex algebraic equations in higher level learning. Of course. The model method is not the only method.. There are many more. It's just one method quite a few of us here like to use.
Also.. When we refer to leaning theories like Skinners or Piaget etc.. We can safely say that proper scaffolding is important for a child's learning. By introducing mechanical ways of working sums to students who need understanding first.. We are skipping the necessary scaffolding our students need for proper understanding...they will score.. But will they remember?
You mentioned the need for a strong foundation.. May I ask.. Which learning theory did you base your pedagogy on?
Definitely.. Using a mechanical way of learning math is going to help our charges score in the exam..not too mention.. It is one of the easier ways...it depends on our motivation.. Either to teach for understanding.. Or to teach for our charges to score.. Either way.. If reflects our beliefs in education...and why we are in it.
Btw..i find it strange you criticise the method but you're on the page..
Either way.. I believe you always have the interests of your students at heart.. Cheers to you my friend.. Have a good Sunday evening

4 years ago

Tan Seng Hoo

I m now a grandpa of 2, my two sons used to be coached by my method and they both excel n have very strong foundation while in their secondary n tertiary education. I m just sharing my interest in Maths. I m now 66 yo

4 years ago

Tan Weiqiang

Thank you Grandpa Tan.. I believe you must be happily retired and enjoying your time with your grandchildren. I wish you good health and happiness.
As mentioned earlier.. I did not criticise your methods.. I questioned..
Nonetheless.. I'm very happy for you that you managed to coach your children to such success. It is indeed enviable.
Thank you for your sharing. I believe many of us younger folks would have learnt a lesson or two from you.

4 years ago

Mary-Anne Rischmueller

It's wonderful you are still sharing your knowledge and love of maths Tan Seng Hoo. Thanks all for your helpful comments

4 years ago

Tan Seng Hoo

U r most welcome. When i sat my PSLE in the early 60s, we used a ble colour textbook General Mathematics for Malayan School where you find standard was almost like sec 1 n 2 level, alot of algebra problem sums, areas and perimeter of squares and rectangle in algebra. See if you can get hold of that book - there are altogether 5 volumes all the way to o level, volume 1 is blue, vol 2 is brown, vol 3 is green, vol 4 is red and last volume is grey. For A maths i think is principle of mechanics

4 years ago

Tan Weiqiang

Would be great if we could get our hands on those books you mentioned Grandpa Tan. Would love to study it to see the evolution of mathematics teaching from the 60s till today.

4 years ago

Tan Seng Hoo

May be write in to some book publishers, scout around in Malaysia, even for grammar, the books we used called Brighter Grammar. Right now if you were to ask a sec 1 pupil to just only give you 10 examples of nouns, adjectives, proverbs or even pronouns, they would have problems. They in turn will ask you what is it you are asking them! You can try. Standards nowadays have dropped compared to my time. Have a nice weekend. Cheers!

4 years ago

Eunice Sng

28 is correct . Maths rule is always do multiplication / division. Follow by +/-

4 years ago

Tan Seng Hoo

Very interesting sharing with fb friends, would like both Mr Tan Weiqiang n Mary Mary-Anne Rischmueller to share other topics, my personal email is tansenghoo@hotmail.com

4 years ago

Tan Weiqiang

Cheers Grandpa Tan. Always a honour to hear our pioneers share. Thank you

4 years ago

Adrian Ng

Asked 7 years ago

SG
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Primary 6
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Number and Algebra