That PSLE maths question!
I have been asking quite a number adults in their mid 20s to 40s if they can solve the following PSLE maths question featured in the papers recently.
The question
Shop A has 156kg of rice. Shop B has 72kg of rice.
After both shops sold an equal amount of rice, the ratio of rice that shop A has to that of shop B is 4:1.
Find the amount of rice sold by the shops.
Many of them was stumped by the question. Most of them said use algebra, but you have remember this is PSLE and even if the child got the answer using algebra, I was told he/she would get 0.
The answer is 44kg.
But it also took me some time to get the answer. I made use of the 4:1 ratio, listed all the multiples of 4 from 4 to 156, subtracted the multiples with the original amount till I got the same difference.
The reason why I am posting is not to show off my maths powers, but it got me thinking that if I have kid who is to take PSLE maths, would I be ready to teach him/her how to get the steps for this answer?
Arithmetic sounds so simple but with questions like this, it makes maths easy.
Maybe Miss Loi, of exampapers.com.sg fame, might want to open up a session for parents on how teach their kids how to solve PSLE maths?
Here’s an alternative answer from JMoss.
Its crazy not to give the kid marks if he/she used algebra to solve. Seriously, what is the point of giving such questions when the most efficient method of solving does not even count. Especially under exam conditions where time does matter.
Then again, PSLE was so long ago for me :p Things really have changed
But you got the answer by trial and error.
In real exam, there isn’t time for such practice.
And you will lose marks on working
Come to think of it… how do you solve this question without trial n error?
Graphically.
Let’s say O represents one fifth of the total rice remaining, and X represents the amount of rice sold by each shop. Then you can draw the following graphical representation of how much rice each shop has to begin with:
Shop A: OOOOX
Shop B: OX
We know OX represents 72kg, and OOOOX represents 156kg. So, OOO must be the difference, which is 84. That means O is 84/3 = 28. And, as we know OX is 72, X must be 72 - 28 = 44.
i believe most primary school children are taught “model drawing”. this method can solve this problem (same method as Lab Rat)
Oh yea, the graphical method of solving things, I guess after primary sch we are so used to algebra that we sort of forgotten about it
Well, I doubt that the child will get a zero since algebra is taught in the syllabus and it is tested in the syllabus. Besides, this question is a simple PSLE math question that can be solved using model system that was taught since P3 or P4.
Its very simple.
Shop A has 4 units + box that signifies amount of rice sold.
Shop B has 1 unit + the same box.
The difference, is 3 units. It can be found by taking 156 - 72. It is not hard to find what 1 unit is, and using 72 to minus the 1 unit, you will get the amount of rice sold by each shop.
This is not difficult for a primary school student to do at all. I am surprised that adults from age 20 to 40 are unable to do it.
I used to tutor a p6 student, thus I know that this is a frequently used method. Hope this helps!
zzz. image didn’t load when i commented.
here’s the image anyway:
http://img529.imageshack.us/img529/542/scan0001tk1.jpg
The question is easy … the schools teach b4 … u are outdated … dun make a big fuss if u are dumb!!!!
@ Hello: Yes, the schools may have taught you how to answer this question.
This post is not about making a big fuss about it or say how difficult it is, but it looks to help parents who are reading this blog to at least try to explain to them how to solve such a question.
I will use the same way as jmoss to ans. That’s what I always do to solve this kind of question, in the past hahaha!
So, this question is supposed to be difficult? I thought it is supposed to differentiate those who are better at such questions. If all the parents make a big fuss about this question, then something is wrong here.
The kids didn’t know how to apply what they have learnt in school.
I asked most of my students, and they told me this question was one of the easiest, not only to my stuents, but to their own classmates.
The ‘key’ to this question is: After selling an Equal amount of rice, the difference of rice they have stays the same! This difference leads to the ratio of 4:1 (we say this as A has 4 units, B has 1 unit, A has 3 units more).
This ‘3 units more’ is the difference between A and B, and this difference does not change becoz they are letting go of the same amount of rice!
my take is that this is a media stunt to raise debate and viewership. These 3 questions, according to my students, were not even remotely the hardest. There was the pattern questions (using ‘n=1′ method) and harder questions that appeared. This is just an act of appeasement…
I see that many people are working towards the answer of 44kg. But when I worked on this question, I have a different interpretation.
“Find the amount of rice sold by the shops.”… I see the answer is 88 kg. If one shop sold 44kg then both shops sold 88kg.
???
@DL: You could be right. The question did ask for the amount of the rice sold by the shops.
I believe Qn 2 is attrocious! The complete answer is in http://coolitan.googlepages.com/pslemaths.htm. (it assumes the rows of 13 and 7 are complete rows, and that “112 more” simply refers to “112 additional chairs than those already described”). You can see you need an A level S paper student to tackle it!
So either the MOE is trying to pick a Pr 6 student who can solve A level S paper questions, or the question is poorly worded. Either that or the paper has published the question wrongly, or the student remembered the wording of the question wrongly.
In terms of wording, are the rows of 7 and 13 chairs or are they partially complete? The usual assumption would be that they are complete and therefore the number divisible by 7 and 13 respectively. Otherwise, there’s no point saying rows of how many. Just say Goup A and Group B.
Secondly, the statement “There are 112 more chairs in rows of 7″ could be ” There are 112 more chairs in addition to those mentioned earlier” but most parents assumed it to mean “There are 112 more chairs in rows of 7 THAN IN ROWS OF 13″. If the latter is what the MOE intended, then the second half should not have been omitted.
At any rate, the answer in the paper 1568 results in incomplete rows of 13. I’m glad I wasn’t one of the PSLE students who sat for the paper. I’d cry on encountering the question!
the paper was somewat Ok.I took it this year,…b4 my psle,I asked 1 teacher 2 teach me sec3 maths..I juz went 4 her tution once 4 2h n I mastered it.almost 1/3 of the paper I use this method…I tink its unfair,,I use sec 3 method 2 solve but it doesn’t mean every1 learns it
Honestly, people are just pissed at how little common sense they have because the difference in weight is not changed.If kids taking PSLE cannot solve this with common sense and a little mathematical manipulation, they don’t deserve their A grade.
Chan’s right. @concussed, the question is wrong. I put up the new question here.
I took the PSLE this year. I think this question is easy because in most schools(at least my school), they have taught us how to solve this question effectively.
Another thing is that I am quite confident that Q2 is wrong. I mean not wrong in the exam papers but I think that the student who was asked, said it wrongly. According to me, it was much harder!
ais,primary maths is reali hard..one of my friends now at a level,last time at sec sch she 1st in the whole sch 4 maths…n guess what,i ask her 2 do my ,maths paper n she cnt solve it,she use all her a level maths strategies n spend more than half an hour but still she failed,she also told me tht she feel tht primary 6 maths is somewat the same level or sometimes even harder than sec maths..
I’ll tell you the real question if you guys want me to.
@Barbie Doll: Please share the real question leh. Thanks.
Some students say the question is hard but as long as u learn the effective method u will know how to do it in a minute.Some methods are like…
(Constant Diff.)for these type of questions . To know this method…
find it out from your teachers…they are COOL! HEY ! be serious PSLE…
REMEMBER >CONSTANT DIFF.!
Umm.. I am a P6 student here and I am taking my PSLE this yr.. Sry to note, but I found this question surprisingly easy…
some of the answers do not sounded logical…
A had 156kg, B has 72 kg.
Same amount of rice sold, hence the deduction from above will be same.
After sales, ratio is 4:1, hence for the 3 parts it is (156-72)kg = 84kg, hence each part is 28kg.
They left a total of 5 parts = 28 x 5 = 140 kg.
As a result, amount of rice sold = (156 + 72) - 140 = 88kg.
This question is sooooooooooooo simple just look at the EQUAL word you kow how to do already. Besides I think that the answer should be 88kg becoz they say find the amount of rice sold by the SHOPS. Anyway I am Jajax and I am in P5 this year. Scared abt PSLE next year!
I am going to give PSLE this year(2008).This is question is a bit confusing but i know how to solve it. Since, they sold an equal amount of rice, the original difference remains the same. The difference is 156-72=84kg. Now the ratio difference is 4-1=3units.Now, that 3units is = 84 kg. Sho B now has left 1unit so it has 84/3 = 28 kg. To find out the rice sold , 72kg(what it had before)-28kg(what it has now)=44 kg. I hope this solves your queries. And one more thing, you CAN USE ALGEBRA.YOU WILL NOT GET A ZERO
heeys! i am not showing off or anything. I am not good in maths but this qns. is seriously simple. I took a while lyk not even 5 mins to figure out. It does nt have to be done with algebra. Just a few steps:
156 - 72 = 84
4:1 = 3u diff. = starting diff.
starting diff = 84
rice sold = 72 - (84/3) = 44kg.
So simple! even my fwen who only got 26 for maths knows how to do it.
anyways. using algebra will also get marks. lols.
Hi. I’m a secondary 4 student. I scored an A* for maths back then. However, it is PERMITTED to use algebra in the PSLE. My sister taught me algebra and simultaneous eqns back then and I used those methods to solve the problems in PSLE. During my prelims, my teachers had no qualms about it and they would mark my methods right. Hence, I went ahead to use algebra and simultaneous eqns during the PSLE exam and I certainly did not do badly.
So cheers! Algebra is actually allowed.
too easy
muhahaha!!!! i have escaped from jail……….and now i am accesable to this website….muhahaha