Tutor MathsGuru: Ask me for your burning Maths questions!

[Dharma]

mathsguru:

Dharma:

Hi mathsguru,


You’re right …. there's an error in qn. Think the cost of 3 watches & 4 rings should be $281 instead of $218.

3W + 4R = 281
4W + 3 R = 342
7W + 7R = 623
1W + 1R = 89
1R = 281 – 3(89) = 14
1W = 89 – 14 = 75

So, 2W + 3R = 2(75) + 3(14) = 192

Cost of 2 watches & 3 rings will be $192.

Hi Dharma,

Ah...so it's $281!! Hehe...you're brilliant!! Thanks for pointing that out~~

Cheers,
MathsGuru

Not brilliant lah, maths guru... 218 + 342 = 560 ...not divisible by 7 ...must be input error!!

[OngMum]

Hi mathsguru, I have a P6 question that needs your assistance to solve.

Looks like model drawing cannot be applied. Time factor is required to be identified. Thanks alot!

Qn : Sulin is given $5 more pocket money than Meihua each week. They each spend $12 per week and save the rest. When Sulin saves $60, Meihua saves $20. How much pocket money does each girl have per week?

[OngMum]

Hi mathsguru, I understand not all qns can be solved by model drawing. Like one qn that my daughter encountered this week, for example needs to adopt check and balance method as there is unknown information. Is there any tips on identify such qns after reading once? Thanks.

[mathsguru]

OngMum:

Hi mathsguru, I have a P6 question that needs your assistance to solve.

Looks like model drawing cannot be applied. Time factor is required to be identified. Thanks alot!

Qn : Sulin is given $5 more pocket money than Meihua each week. They each spend $12 per week and save the rest. When Sulin saves $60, Meihua saves $20. How much pocket money does each girl have per week?

Hi OngMum,

Here's my solution. Though drawing models is not a must, I feel that drawing out models helps me in visualising the problem better. For instance, after drawing out the models, I can see clearly that the difference between their savings is $5 per week.

http://www.postimage.org/image.php?v=Pq1x0wNA

Cheers,
MathsGuru

[mathsguru]

OngMum:

Hi mathsguru, I understand not all qns can be solved by model drawing. Like one qn that my daughter encountered this week, for example needs to adopt check and balance method as there is unknown information. Is there any tips on identify such qns after reading once? Thanks.

Hi OngMum,

I do agree that not all questions can be solved by model/diagram drawing. Sometimes, there's no need for it or sometimes, it is simply of no help.

Although I can't spell out all the criteria for identifying a question which needs models/diagram, I can list down some that I can think of right now:
1. When ratio or fractions or percentage or age is involved
2. \"Before and after\" questions involving the above topics (e.g. give some sweets away to another person, some men left and some women entered the room and then the ratio changed, etc)
3. Comparison question involving 2 or more people and their items (e.g. A has 12 marbles more than B and C has 10 marbles more than B. Total = 70 marbles.)
4. Certain speed questions (these are usually more of diagrams to visualise rather than unitary models)
5. When questions have phrases like \"twice as much\", \"thrice as much\", \"half of\", etc.
6. Certain money problems, especially when it's a complicated question that has a bit of info on quantity and a bit of info on value (e.g. Went shopping with $360. Bought some shirts and skirts. Had $8.50 left. Bought 3 fewer skirts than shirts. Each skirt is $15.50 more than a shirt. How many shirts was bought?)

Hope you can relate to the types of questions I described above!

Just to add, many students find ratio/fraction/% questions more challenging and they usually get stuck in trying to draw out the models. And (unfortunately!) for these topics, models are usually the best way to solve the problems since simultaneous equations are not taught in Primary School. I guess that's why you find me using diagrams/models alot in my solutions because the questions posted are all mostly from these topics.

Well, in any case, for most questions, I usually encourage my students to use \"guess & check\" as the last resort. Even for questions like \"There are 85 rabbits and chickens in a farm. Ali counted 220 legs in total. How many rabbits and how many chickens are there?\", there's no need to use guess & check or models. We can use logic to deduce the correct answer in just 3-4 steps.

So, in my personal opinion, there's no hard & fast rule in solving maths questions. There're usually at least a couple of methods that we can use - just that there may be one that is simpler/shorter.

All I can say is the more types of questions we're exposed to through practice, the more adept we become in identifying the best methods to use to solve them. Hee...I guess there's no short cut in the pursuit of excellence...

Cheers,
MathsGuru

[OngMum]

Thank you so much for solving the qn, mathsguru.

And thank you also for sharing your take on how to identify different types of qns. Appreciate it! :thankyou:

[kitty2]

mathsguru :?: ,thank you.May i know what's the trick for such questions and how to solve them in a faster way?



Diagram 1 2 3 4 5

1)Number of shaded squares 1 5 9 13 17
Number of unshaded squares 0 4 16 36 64
Total number of squares 1 9 25 49 81

a) Write down the total number of squares in Digram 30

b) Find the total number of unsquares in Digram 50

c)Write down the number of digram that has 29 shaded squares.


2)For 1 step stairway,1 brick is used.For a 2 step stairway,4 bricks are used and so on

a)Write down the number of bricks used for a 5 step stairway
b)write down the number of bricks used for a 40 step stairway
c)Find the number of steps if a total of 144 bricks are used
d)Find the number of steps if a total of 576 bricks are used

[Daddy]

Hi,


I have Math question need help.

A 3-digit number when divided by 5 gives an even number. When it is divided by 3, it also gives an even numbers.
(a) What is the digit in the ones place?
(b) What can be the number be?

Thanks :?

[Muffins]

Daddy:

Hi,


I have Math question need help.

A 3-digit number when divided by 5 gives an even number. When it is divided by 3, it also gives an even numbers.
(a) What is the digit in the ones place?
(b) What can be the number be?

Thanks :?

Hi Daddy, for a), the answer is 0 as 0 & 5 are the only numbers that when divided give a whole number, but 5, when divided, always gives an odd number at the end e.g. 25 divided by 5 is 5, but ten divided by five is two, so the first answer is 0. For b), the number could be a lot of numbers, but the first one that popped into my head is 420. 420 divided by 5 gives you 84, and 420 divided by three gives you 140. So it is accurate.

Hope I helped!

[Daddy]

Thanks,


But for question (b) only one number.