Tutor MathsGuru: Ask me for your burning Maths questions!

[Dharma]

meimeitan:

Hi Maths Guru


There is a Math question as following:

There were 12 more girls than boys in a club. 1/3 of the girls and 1/4 of the boys took part in a competition. Among those who took part in the competition, there were 6 more girls than boys. What fraction of the club members who did not take part in the competition were boys?

May I know the meaning of \"What fraction of the club members who did not take part in the competition were boys.?\" The denominator should be the whole club members or the club members who did not join the competition.

Thanks

Hi May I know who can solve my doubt? Thanks.

It means the proportion of the total number of members who are boys and did not take part in the competition.

The denominator => Total club members

[ADoc]

meimeitan:

Hi Maths Guru


....May I know the meaning of \"What fraction of the club members who did not take part in the competition were boys.?\" The denominator should be the whole club members or the club members who did not join the competition...

Hi there! I shall take the plunge.

From a grammar perspective, the denominator would be \"club members who did not join the competition\", since the relative pronoun \"who\" is used to introduce a further comment or description of an earlier person or group of persons. That means the question is restricting the club members to be just those who did not take part in the competition.

Compare with \"What fraction of those, who did not take part in the competition, were boys?\" Would this be clearer?

If I were to re-phrase the question: \"What fraction of the club members were boys who did not take part in the competition?\"; the denominator would be total club members since this time round, the \"who\" is used to describe the boys and not the total club members.

Anyway, I totally understand how frustrating it can be sometimes, having to dissect a primary-level mathematical question with such ambiguity. I consider this question to be fairly straightforward. I'm sure you have come across even more ambiguous questions in the course of guiding your kids.

Check out RazorTV for the segment on PSLE math. It's hilarious how FD was ridiculing the way PSLE math problem sums are phrased.

Hope this helps.

[Bunny27]

Hi Maths Guru,


Need help for 2 questions:

a) mrs lee baked 60 more pies than mrs tan. After mrs tan gave 30 pies to mrs lee, mrs lee has twice as many pies as mrs tan. How many pies had mrs lee at first?

b)The table shows the number of students from class 5P scoring various mark ranges in a mathematics test. Part of the table was dirtied by some ink.

91-100 - 10 students
81-90 - 8 students
71-80
61-70
51-60
30 students scored above 70 marks
how many studens scored in the mark range 71-80?

[andante]

ADoc:

andante:

...using algebra simultaneous equations but I heard that the pupils cannot use this method to solve during PSLE exam or else marks will be deducted...

Hi there! Sorry for the repetition. Since we have \"new\" PSLE moms & dads every year, guess this piece of info would serve well to many.

Here's an excerpt from the \"Forum Letter Replies\" by MOE & SEAB on \"Different Approaches Taught for Mathematics Techniques\":

\"....While pupils are not required to use algebra to solve word problems in the PSLE Mathematics, they are also not restricted to the use of any one particular method. In the marking of PSLE Mathematics, all mathematically correct solutions are acceptable and there is no loss of marks if a correct algebraic method is used.\"
See http://www.moe.gov.sg/media/forum/2007/20070217.htm

Hope this clarifies your doubt. Notwithstanding MOE's and SEAB's endorsement, parents need to ensure their kids are able to internalise and apply what you have explained / taught them about algebraic solutions, instead of merely understanding. Else they may be extremely confused. There's a good reason why the primary curriculum limits the extent of algebraic teachings; not all students are able to grasp the seemingly abstract concepts of x, y, & z, even though algebra is already masked in the form of Models & Units.

Just a quick suggestion: More often than not, the algebraic approach can be \"transformed\" to the model approach. For example, instead of saying \"let x be...\", we can always draw a certain length of model to represent the same thing. Remember that model is algebra in disguise.

Of cos, if your kid is quick at grasping advanced concepts, do go ahead and use algebra. I have taught my students algebra and encourage those confident enough to use them in PSLE. Confirmations with past students using algebra obtained A* with no problems at all. Perhaps this can be another instance to nullify the hear-say that algebra will result in loss of marks.

cheers!
ADoc

Hi,
Thank you for your reply. I hope you can help to solve the problem using model approach.

Thanks and regards,

[CJM]

To motivate her son to study mathematics, Mrs Mani agreed to reward her son 50 cents for every problem solved correctly and to fine him 35 cents for each incorrect solution. At the end of 17 problems, neither owed anything to the other. How many problems did her son solve correctly?

[CJM]

the tickets for a show are priced at $22 and $8. The number of $12 tickets available is 1 1/2 times the number of $8 tickets. 2/3 of the twelve-dollar tickets and the eight-dollar tickets were sold. The ticket sales amounted to $6400. How much more would have been collected if all the tickets were sold ?

[iFruit]

ADoc:

meimeitan:

Hi Maths Guru


....May I know the meaning of \"What fraction of the club members who did not take part in the competition were boys.?\" The denominator should be the whole club members or the club members who did not join the competition...

Hi there! I shall take the plunge.

From a grammar perspective, the denominator would be \"club members who did not join the competition\", since the relative pronoun \"who\" is used to introduce a further comment or description of an earlier person or group of persons.

I agree. The denominator should be \"club members who did not join the competition\".

[small]

CJM:

To motivate her son to study mathematics, Mrs Mani agreed to reward her son 50 cents for every problem solved correctly and to fine him 35 cents for each incorrect solution. At the end of 17 problems, neither owed anything to the other. How many problems did her son solve correctly?

Please try to use guess and check method.

From working,her son solved 7 problemd correctly.

[atutor2001]

small:

CJM:

To motivate her son to study mathematics, Mrs Mani agreed to reward her son 50 cents for every problem solved correctly and to fine him 35 cents for each incorrect solution. At the end of 17 problems, neither owed anything to the other. How many problems did her son solve correctly?

Please try to use guess and check method.

From working,her son solved 7 problemd correctly.

I recommend \"replacement method\". This is a 3 mark question and guess and check might take too much time.

If the son gets all correct : 17 x 50 = 850
For every 1 wrong, the son must return 50 + fine 35 = 85

At the end, the son gets nothing means he return 85 cents 10 times. (850/85 = 10) That is, he got 10 wrong. Therefore, no. of correct is 7.

[NickleBee Tutors]

andante:

Pls help for the following question. I have solved it using algebra simultaneous equations but I heard that the pupils cannot use this method to solve during PSLE exam or else marks will be deducted.



20% of the number of balls Kyle had is equal to the 35% of the number Pauline had. After Kyle sold another 30 marbles and Pauline bought 20 marbles, 30% of the number of marbles Kyle had is equal to the 50% of the number Pauline had. What is the number of marbles each of them had at first?

Thanks in advance

During the \"parents meet teachers\" sessions for Pri 5 and 6 pupils, the oft-mentioned query on whether algebra is accepted in the PSLE maths paper is very commonly posed by anxious parents.

Most Primary School mathematics teacher will parrot MOE's stand that \"In the marking of PSLE Mathematics, all mathematically correct solutions are acceptable and there is no loss of marks if a correct algebraic method is used.\"

That being said, Primary school maths teachers and PSLE markers will also highlight the fact that what they are looking for is the ability of the child to show that he understands the context of the problem sum and is able to apply an appropriate method to reason and solve it in a logical and sequential manner.

Now as i understand from my chats with primary school teachers, for a 5 mark question, 4 marks are method marks and a correct answer is allocated 1 mark. So the marker will go down the question and tick each sequential step off if the marker is satisfied that the child is on the right logic/reasoning track. Anyway just to share, if the child makes a careless mistake right at the first step, and yet all his remaining steps are logical and shows that he understands the question and has applied proper reasoning to solving the question, he would of course not get the 1 answer mark (because the answer will definitely be wrong) but he may be able to get all 4 method marks!

If algebra is used and if it is done perfectly and with proper application to the question, i am sure the examiner is more than willing to award the full 5 marks. But if the PSLE marker is unsure and errs on the side of caution by bouncing the script up to the supervisor to rule on whether the algebra is acceptable. If they still find it unacceptable because they cannot be sure that the child has truly understood the context of the question and shown how he has arrived at the answer in a logical manner, then i guess its up to the supervisor on how many marks can be awarded.

Another point to note. More often than not, unless the child is very well grounded in algebra, careless mistakes and wrong application of algebraic concepts will lead to a wrong answer (1 mark gone). Also, most of the algebraic statements as written will become grossly off tangent as well and are no longer answering the question, and the child will start to lose all his method marks as well.

So the impression i get is that MOE accepts algebra but to be fair to those using other problem solving methods, it is marked to the same rigorous standard as the rest of the cohort. If the child uses algebra and is unable to demonstrate his understanding of the question and proper application of his chosen method which allows the marker to be satisfied that the child can solve the question with acceptable reasoning and logical thought processes, the marker has every right to decide how many marks are to be awarded. This gives rise to the misconception that marks will automatically be deducted once algebra is used. That is not true.

Now, i would like to re-emphasize the fact that throughout the Primary School syllabus, pupils are taught various problem solving skills, approaches and heuristics to solving maths problems. And most if not all of the PSLE questions can be solved by understanding the context of the question, applying reasoning and procedural knowledge. So as i tell my students, why give the marker an excuse not to award you any marks?

Yours
Zhou Shicai
NickleBee Tutors