Tutor MathsGuru: Ask me for your burning Maths questions!

[maths6a]

Dear all,

Wrt the speed qn, now that someone explained that 1u is the average of the speed he’s travelling so + 10 and -10 will be the speed he was well and sick, I can now understand the solution.

But why is it when I use
40/x - 40/x +20 = 1/6 (x being the speed when he was not well and x + 20 being the speed when he was well), then I cannot solve from here?

I think one has to be very familiar with algebra to be able to use algebra but this is like way beyond a 12 year old?

I think in this case maybe the guess and check method is a better choice especially after one has spent some time trying to work out the various possible methods?
Thanks in advance for the time to explain.

[atutor2001]

maths6a:

Dear all,

Wrt the speed qn, now that someone explained that 1u is the average of the speed he's travelling so + 10 and -10 will be the speed he was well and sick, I can now understand the solution.

But why is it when I use
40/x - 40/x +20 = 1/6 (x being the speed when he was not well and x + 20 being the speed when he was well), then I cannot solve from here?

I think one has to be very familiar with algebra to be able to use algebra but this is like way beyond a 12 year old?

I think in this case maybe the guess and check method is a better choice especially after one has spent some time trying to work out the various possible methods?
Thanks in advance for the time to explain.

You can still solve using (x+20), giving x = 60 or -80 (rejected because negative)

The use of (x+10) & (x-10) is a shortcut which only those very well versed with math will know how to capitalise, to simplify computation.

This method is beyond P6. I think Quadratic & Factorising is taught only in Sec 2. So do not spend time on it unless you are crazy over math.

[Dharma]

Kiasu Friend:

ABCDE:

[quote=\"Kiasu Friend\"]
Hi Dharma,

Thank you very much for the algebra solution. I can readily understand it and also somehow feel more comfortable with it.

However, as others have pointed out earlier, 'Guess & Check' seems to be a workable option that can be resorted to. But, as Tianzhu mentioned, one needs a 'number sense' to make smart guesses. I am yet to develop that skill.

Thanks and regards.

Hi Kaisu Friend,
Can u explain the algebra method used..I blur on what is 1u assumed as...
TIA

Hi ABCDE,

1u stands for the average of the two speeds, i.e., the usual speed of Tom and the slower speed at which Tom drives when he is sick.

I can explain the solution in more detail, but I think it is better that you request Dharma to explain it because:

(a) He is the author of the excellent algebra solution provided above
(b) I consider him an 'authority' on this when compared to an amateur like me.

Thanks and Regards.[/quote]Hi Kiasu Friend,

Please do not consider me an “authority” in maths and because I’m not one and I don’t deserve to be called that. I’m another parent just like most of you here and I am just trying to share whatever I know and at the same time learn new things here in this forum.

For the speed question, I just provided an alternative and I had qualified my solution by stating that it was meant for pupils who are familiar with algebra. Guess and check is always a great way to find the answer, if you do not know the correct method to use. For P6 kids, my advise is if you are stuck with a problem and do not know how to solve and if you resort to Guess and Check method and get the correct answer; you will get the full marks. Although, Guess and Check is not as elegant as some of the other heuristics but who cares in PSLE if your working is not elegant enough, especially when you under pressure to solve the problem that you have trouble with, don’t waste too much time thinking about the method, Guess and Check will get you the full marks (if your answer is correct). That was what I advise my dd2 last year.

Coming to the speed question, you are right that I chose 1u to be the average speed of Tom’s usual speed and Tom’s speed when he was sick.

(A + B) x (A – B) = A^2 – B^2

So,
(1u + 10)(1u – 10) = 1u^2 - 100
Then, we just find the difference in time taken when Tom was sick and when he was well (using distance divided by time) which will equal to 1/6 hour.

Solve the equation to get 1u.
To find Tom’s usual speed; you have to add 10km/h to 1u to get 80km/h

Thanks

[Herbie]

I have the following qns which needs help


SCGS
1. Mr Tan had 130 durians and mangosteens. After he sold 2/3 of the durians and 2/5 of the mangosteens. he had 36 more mangosteens than durians left. How many fruits had he left in all?

2. Tracy counted the number of 10cents coins, 20 cents coins and 50 cents coins in her piggy bank. The no. of 10cents coins was 24 more than the no. of the number of 50 cents coins. After spending 3/5 of the 10 cents coins, 1/4 of the 20 cents coins and 18 50 cents coins, she had an equal no. of 10 cents and 20 cents coins. The no. of 50 cents coins now formed 40% of the remaining number of coins.

How many 10 cents coins did Tracy have at first?
How much did she spend in all?

3. Ahmad and Halim together took 5 days o paint their house. If Ahmad and Halim work together for 2 dys, followed by Ahmad working alone for 8 days, Halim will take 1 more day to complete the remaining work. How long will Ahamd take to paint the house all by himself?

Thanks!

[Vanilla Cake]

Herbie:

I have the following qns which needs help


SCGS
1. Mr Tan had 130 durians and mangosteens. After he sold 2/3 of the durians and 2/5 of the mangosteens. he had 36 more mangosteens than durians left. How many fruits had he left in all?

2. Tracy counted the number of 10cents coins, 20 cents coins and 50 cents coins in her piggy bank. The no. of 10cents coins was 24 more than the no. of the number of 50 cents coins. After spending 3/5 of the 10 cents coins, 1/4 of the 20 cents coins and 18 50 cents coins, she had an equal no. of 10 cents and 20 cents coins. The no. of 50 cents coins now formed 40% of the remaining number of coins.

How many 10 cents coins did Tracy have at first?
How much did she spend in all?

3. Ahmad and Halim together took 5 days o paint their house. If Ahmad and Halim work together for 2 dys, followed by Ahmad working alone for 8 days, Halim will take 1 more day to complete the remaining work. How long will Ahamd take to paint the house all by himself?

Thanks!

Pls refer to this http://www.onsponge.com/forum/35-thinkingmathonsponge/3109-p6-prelim-paper-last-year-help.html#3128.

[Ngserene617]

mathsguru:

Original Title: Let MathsGuru Answer Your Burning Maths Questions!


Hi,

I need help for this question:
1. Jimmy collected 889 apples. Haley collected 167 apples. How many apples must Jimmy give to her so that he would have thrice as many apples as Haley?

Thanks !

:welcome:

Dear Parents,

Are you frustrated/stuck when helping your child solve his/her Maths questions? Are you inclined to use Algebra most of the time? Do you have difficulty trying to use diagrams or other heuristic methods (that Primary School students learn) to solve?

:idea: Post your questions here and see how MathsGuru solve them to the best of her ability. Detailed solutions will be posted back in this thread.

So start asking and watch this space!!

Cheers :celebrate: ,
MathsGuru

P/S (Disclaimer, in case you're wondering...):
Although MathsGuru is a full-time Maths tutor, this thread is meant to be an absolutely free resource for parents (or even children) with no strings attached. Just someone who's passionate about Maths and wanna spread the fun in learning Maths with others.

[Ngserene617]

mathsguru:

Original Title: Let MathsGuru Answer Your Burning Maths Questions!


:welcome:

Dear Parents,

Are you frustrated/stuck when helping your child solve his/her Maths questions? Are you inclined to use Algebra most of the time? Do you have difficulty trying to use diagrams or other heuristic methods (that Primary School students learn) to solve?

:idea: Post your questions here and see how MathsGuru solve them to the best of her ability. Detailed solutions will be posted back in this thread.

Hi MathsGuru,

pls help me this question;
1. Jimmy collected 889 apples. Haley collected 167 apples. How many apples must Jimmy give to her so that he would have thrice as many apples as Haley?




So start asking and watch this space!!

Cheers :celebrate: ,
MathsGuru

P/S (Disclaimer, in case you're wondering...):
Although MathsGuru is a full-time Maths tutor, this thread is meant to be an absolutely free resource for parents (or even children) with no strings attached. Just someone who's passionate about Maths and wanna spread the fun in learning Maths with others.

[livewith_vanilla]

Ngserene617:

mathsguru:

Original Title: Let MathsGuru Answer Your Burning Maths Questions!


Hi,

I need help for this question:
1. Jimmy collected 889 apples. Haley collected 167 apples. How many apples must Jimmy give to her so that he would have thrice as many apples as Haley?

Thanks !

:welcome:

Dear Parents,

Are you frustrated/stuck when helping your child solve his/her Maths questions? Are you inclined to use Algebra most of the time? Do you have difficulty trying to use diagrams or other heuristic methods (that Primary School students learn) to solve?

:idea: Post your questions here and see how MathsGuru solve them to the best of her ability. Detailed solutions will be posted back in this thread.

So start asking and watch this space!!

Cheers :celebrate: ,
MathsGuru

P/S (Disclaimer, in case you're wondering...):
Although MathsGuru is a full-time Maths tutor, this thread is meant to be an absolutely free resource for parents (or even children) with no strings attached. Just someone who's passionate about Maths and wanna spread the fun in learning Maths with others.

Hello!

Okay, for your questions, here's my solution:

Since the total apples will remain the same no matter how many apples are exchanged between Jimmy and Haley, the first step is to find the total number of apples collected by both Haley and Jimmy.

889+167=1056

There are 1056 apples in total.

In the end, the question wants Jimmy to have 3 u and Haley to have 1u.

3u+1u=4u
1056/4=264

Haley should have 264 apples in the end.
However she has 167 apples only.

Thus,

264-167=97

Jimmy would have to give Haley 97 apples so Haley would have 264 apples and Jimmy would have three times as many apples as Haley.

[Herbie]

Thanks Vanilla Cake for the link. Many thanks!

[laikiasu]

Hi Mathsgurus out there,


Qn: Mrs Ong owns 3 dogs. Each dog gave birth to 3 puppies and when the puppies grew up, they each gave birth to 3 puppies. How many dogs does Mrs Ong own now?
Ans: 18 (found in answer page) but my own answer was 39.

Can you help tell me how to get 18? Or is there a printing error in the answer page?

Thanks.

Rgds,
laikiasu