Tutor MathsGuru: Ask me for your burning Maths questions!

[pokemon]

[quote]Going by what you mentioned in your posting, your son's method is not very correct even though he ended up with the correct answer. And it is very important to clear his misconception esp. since he's only in P1 now.


The reason why I say his method is not right is because his reasoning for obtaining 9 toy cars is not logical (\"He come out with 4+9=13 for toy soldiers,therefore toy cars = 9 initially\"). There's no information in the question which can lead us to find out how many toy cars or soldiers there are initially. The information is all about the difference in numbers. [/quote]
tks mathsguru, i fully understand your explaination. u have actually confirm my guesses that my boy is nt that correct. i also thought he shdnt add the number directly ie 4+9=13,he sort of interpreted the problem sum in his own way,in his own world. Im afraid due to his young age may hv problem understanding my explaination. Nevertheless, it prepare me for future question shd he solve it in tis manner.

[pokemon]

Muffins:

Hi pokemon, can't believe your son is only Primary 1, it took a Sec 1 student a while to understand his method! WOW! You have a very smart son there! [img]

Muffins,
thank you,but his answer, as u can see mathsguru explaination, is not that right but its a good try for him. Tis type of question is v common in pri sch, probably Sec1 student may hv forgotten liao

[Muffins]

Hi pokemon, I haven’t forgotten ( :x ) but, I understand your son’s method as I use algebra to solve problems, though mathsguru uses models.

[pokemon]

Muffins:

Hi pokemon, I haven't forgotten ( :x ) but, I understand your son's method as I use algebra to solve problems, though mathsguru uses models.

Talk about using algebra, some questions my son will sort of use algebra method though nobody taught him :? , even my elder sec sch son also said the same like you. My elder boy v happy now cos in sec sch no need to use model,juz apply algebra.

[YLH88]

Hi Mathsguru,


Need your help in the following questions :

1) In a mathematics competition with 100 participants, the average score was 63. Given that the average score of the boys was 60 and that of the girls was 70, find the number of boys and that of girls who participated in the competition.

2) Tom's present age is thrice Sally's age some years ago. Conversely, Sally's present age is Tom's age the same number of years ago. Given that the sum of their present ages is 30 years, how old is Tom now ?

3) When Kok Hwa's age was twice Bala's age, Mike's age was 30. When MIke's age was twice Kok Hwa's age, Bala's age was 21. Given that Mike was the oldest among the three persons, find Bala's age when Mike was 62 years old.

Thank you very much

[mathsguru]

YLH88:

Hi Mathsguru,


Need your help in the following questions :

1) In a mathematics competition with 100 participants, the average score was 63. Given that the average score of the boys was 60 and that of the girls was 70, find the number of boys and that of girls who participated in the competition.

2) Tom's present age is thrice Sally's age some years ago. Conversely, Sally's present age is Tom's age the same number of years ago. Given that the sum of their present ages is 30 years, how old is Tom now ?

3) When Kok Hwa's age was twice Bala's age, Mike's age was 30. When MIke's age was twice Kok Hwa's age, Bala's age was 21. Given that Mike was the oldest among the three persons, find Bala's age when Mike was 62 years old.

Thank you very much

Hi YLH88,

Here are my solutions.

http://www.postimage.org/image.php?v=gxeRI1A

http://www.postimage.org/image.php?v=gxeRKwJ

http://www.postimage.org/image.php?v=gxeRFxr

Cheers,
MathsGuru

[mathsguru]

pokemon:

Muffins:

Hi pokemon, I haven't forgotten ( :x ) but, I understand your son's method as I use algebra to solve problems, though mathsguru uses models.

Talk about using algebra, some questions my son will sort of use algebra method though nobody taught him :? , even my elder sec sch son also said the same like you. My elder boy v happy now cos in sec sch no need to use model,juz apply algebra.

Actually, to a certain extent, model diagrams used in those challenging problems (esp. ratio/fractions) are in essence simultaneous equations at work!

Just try to notice it the next time you encounter the more \"complex\" diagrams. For e.g. whenever we express 1 item in terms of another item, we are actually doing substitution method (in algebra), just that it's easier for primary school students to \"visualise\" with the aid of diagrams than to use \"x\" and \"y\"...

My 2 cents' worth,
MathsGuru

[YLH88]

Hi Mathsguru,


Thank you very much for your prompt reply.

But hor, don’t quite understand the solution for question 2. I don’t understand how you get the 3rd set of diagram with the yellow box. How come is 1/3 of Tom’s present age ? and how to get the 5 units ?

Many thanks!

Regards
Jasmine

[thinkingmath]

YLH88:

1) In a mathematics competition with 100 participants, the average score was 63. Given that the average score of the boys was 60 and that of the girls was 70, find the number of boys and that of girls who participated in the competition.

Hi YLH88

Another method removing \"the guess work\" that we sometimes teach our students is using a method we call Number of Units x Value of Units. Our P3 books introduce this method very successfully, however, most questions would not have negative numbers involved. Given this is related to Average, this question will be at least P5 and at this Level our students will have no problem using Number of Units x Value of Units for this question. The advantage is that it removes any guess work and is an more efficient approach.

http://www.onsponge.com/pub_images/onsponge_number_value_20100120.jpg\">

[Dharma]

YLH888,


This is another approach to solve the age problem.

http://www.postimage.org/image.php?v=Tsyojsi