Tutor MathsGuru: Ask me for your burning Maths questions!

[Dharma]

tianzhu:

Hi Dharma


This question is quite similar to Rosyth 2008 SA2 Q48.

Ning and Zongwei jogged to and fro repeatedly along a straight path in a park between two points A and
B. Ning jogged at a uniform speed of 4 m/s and Zongwei jogged at a uniform speed of 6 m/s. They
started jogging from opposite directions at the same time as shown below.
They first met one another at point X. The second time they met was at point Y.
a) Given that the distance between X and Y is 160m. Find the distance between A and B.
b) If they started jogging at 8 am, how long did they take to meet again for the third time? (Express
answers in min and seconds).

However in the Rosyth question, the speed ratios are given.

In this question, the speeds of Raju and Ali are not given.

Do we have to make an assumption that they turn at the third interval of time?

Best wishes.

In the Rosyth 2008 qn, part (b) requires the pupil to calculate the time taken for Ning and Zoingwei to meet to for the 3rd time. However, the current question only talks about Raju and Ali meeting twice. So, we don’t need to assume that they turn around for the 3rd time.

Both questions are similar but the information given in both questions are different. Rosyth qns gives the speed of the 2 persons and the distance between the meeting points, X and Y while the current question requires us to find out the distance between the 2 meeting points.

[tianzhu]

Hi Dharma


Thank you for your reply.

I think we are not talking about the same thing. I am sorry for not making it clear in my earlier post.

Let’s not focus in what were asked to find in the Rosyth question.

I brought it up to show the similarity between the Rosyth and the new question in certain aspects.

The ratios in one question are given while in the other, they are not.

If the speed ratios are given, a student can easily show that they would meet at the third period of time.

The question is how does one knows that they’ll meet at the third period of time if the speed ratios are not given?

In the third interval of time, Raju makes a U turn, do we assume that he does it at the third period?

If we make an assumption that they would meet at the third period of time, then this question could be solved with visual representation by showing a distance line.

Best wishes

[Dharma]

tianzhu:

Hi Dharma


Thank you for your reply.

I think we are not talking about the same thing. I am sorry for not making it clear in my earlier post.

Let’s not focus in what were asked to find in the Rosyth question.

I brought it up to show the similarity between the Rosyth and the new question in certain aspects.

The ratios in one question are given while in the other, they are not.

If the speed ratios are given, a student can easily show that they would meet at the third period of time.

The question is how does one knows that they’ll meet at the third period of time if the speed ratios are not given?

In the third interval of time, Raju makes a U turn, do we assume that he does it at the third period?

If we make an assumption that they would meet at the third period of time, then this question could be solved with visual representation by showing a distance line.

Best wishes

Hi Tianzhu,

For this question, when they meet for the 1st time, both take the same time (fixed time).
We found out that Town A to P is 10km and Town B to P is 13km. So, the distance ratio of Raju : Ali = 10 : 13 and their speed ratio will also be 10 : 13. The speed ratios will ontinue to be the same so long as they do not change their speeds.

They will meet for the 3rd time, 4th time and so on if they continue moving back and forth between Town A and Town B.

If they set off from the same point but in opposite directions, their total distance from the time they move to the time they meet again will be twice the sum of the total distance of Town A and Town B.

“ In the third interval of time, Raju makes a U turn, do we assume that he does it at the third period? “.Yes.

If they continue their travelling they will meet at Point R which is 4km from Town A and it can be seen by drawing a distance line.

[tianzhu]

Dharma:

“ In the third interval of time, Raju makes a U turn, do we assume that he does it at the third period? “.Yes.

Hi Dharma

Thank you for your reply.

The starting point is to make an assumption that they turn at the third period of time.

Once a student is able to do it, this question could be easily solved by drawing a distance line.

Best wishes

[peapot]

Hi, I have encounter a P1 math problem. Please see pic below. I found out the answer by trial and error but is there a systematic approach to solve this question. I do not understand how to teach my P1 gal on this type of question. Please help me!

Thanks!!


http://postimage.org/image/3393pe1s4/
[/img]

[Dharma]

peapot:

Hi, I have encounter a P1 math problem. Please see pic below. I found out the answer by trial and error but is there a systematic approach to solve this question. I do not understand how to teach my P1 gal on this type of question. Please help me!

Thanks!!


http://postimage.org/image/3393pe1s4/
[/img]

Find the number bonds of 11

6 + 4 + 1
6 + 3 + 2
5 + 4 + 2

The numbers 2, 4 and 6 appear twice. These numbers must be placed at the corners and 1,3 and 5 will be the middle numbers.

[peapot]

Thanks for you help. But I still don’t quite get it. Why those numbers appear twice must by placed in the corner circle? Hmmm…is there any rule I can follow to explain why the numbers appear twice must be place in the corner?


Pardon me but my maths was quite lousy why I was younger.

[rubydoll]

My son told the maths paper was easy.

I thank the mathsguru team and esp Mr Dharma and Sweet girl vanilla cake for the marvellous work in helping us understand the sums.
Thank you again.
GOD BLESS YOU ALL.

[Dharma]

peapot:

Thanks for you help. But I still don't quite get it. Why those numbers appear twice must by placed in the corner circle? Hmmm.....is there any rule I can follow to explain why the numbers appear twice must be place in the corner?


Pardon me but my maths was quite lousy why I was younger.

Number that appear twice in the number bonds abovve is shared between 2 sides of the triangle. If u place 6 at the top most circle, 6 is common to the number bonds on the 2 sides of the triangle.

Similarly, 2 and 4 will have be shared by 2 different number bonds. Draw the numbers on the circle and you will see it clearly.

[Dharma]

rubydoll:

My son told the maths paper was easy.

I thank the mathsguru team and esp Mr Dharma and Sweet girl vanilla cake for the marvellous work in helping us understand the sums.
Thank you again.
GOD BLESS YOU ALL.

Hi rubydoll,

It is nice hear that your son found the paper easy and best wishes to him.