Q&A - PSLE Math

[acforfamily]

suiyuan:

Thank You for your help.

Please help me solve these questions in a non-algebraic manner.

Q1) A motorist takes 1/2 h less than the usual time to travel from KTown to JTown when he increases his average speed by 10%. For a distance of 100km, he will take 1/3 h less than the usual time if his speed is 20% more than the average speed from KTown to JTown. Find the distance between KTown and JTown.

Q2) A car travels from town P to town Q at a constant speed. When it increases its speed by 20%, the journey from P to Q takes 1 hour less than its usual time. When it travels at its usual speed for 100 km before increasing its speed by 30%, the journey also takes 1 hour less than usual. Find the distance between the two towns.

hi suiyuan,
i think the answers are found here
http://prischoolmaths.blogspot.com/search/label/Maths-Speed

[N3SKiasu]

Dear Dharma, thanks for solving my earlier question.


I have one Q :
2 groups of people, A and B are working on a project. If 18 people move from group A to group B, then group B will have 3 more people than group A. If we take away 18 people from both groups, then the remaining people in group B is 5/8 of that of group A. Find the number of people in each group at first. (Ans :106 and 73).

I managed to solve the above using Model, but it is rather complex. I wld like to seek your advice whether/how above can be solved by your usual Units/Parts method. Appreciate if you cld enlighten.

Btw, my earlier question
In a classroom, when a boy stands up, the number of boys sitting becomes 4/5 of the number of girls sitting. On the other hand, when a girl stands up, the number of girls sitting becomes 8/7 of the number of boys sitting. How many boys and girls are there in the class altogether?

Your answer contained:
3u=5p
1u = 5 & 1p=3

May I kw how is the last step being deduced from the earlier step?
Sorry if this question sound silly, I think I obviously unable to grab an impt concept here, :oops: wld appreciate your enlightenment.

Thks very much Dharma, for your help.

[tianzhu]

N3SKiasu:

2 groups of people, A and B are working on a project. If 18 people move from group A to group B, then group B will have 3 more people than group A. If we take away 18 people from both groups, then the remaining people in group B is 5/8 of that of group A. Find the number of people in each group at first. (Ans :106 and 73).

I managed to solve the above using Model, but it is rather complex.

Hi
Just trying to understand why did you say MD is rather complex to be used to solve this question.You may wish to share your MD.

[N3SKiasu]

tianzhu:

N3SKiasu:

2 groups of people, A and B are working on a project. If 18 people move from group A to group B, then group B will have 3 more people than group A. If we take away 18 people from both groups, then the remaining people in group B is 5/8 of that of group A. Find the number of people in each group at first. (Ans :106 and 73).

I managed to solve the above using Model, but it is rather complex.

Hi
Just trying to understand why did you say MD is rather complex to be used to solve this question.You may wish to share your MD.

Hi Tianzhu,
oh..it looks rather complex to me if I try to use it to explain to my child so I wld like to learn a simpler mehod from Dharma, if there is.

I wld very much like to share the MD at the same time, the drawing is just lying in front of me! but I am struggling to put the diagram into words. sorry very poor in this sort of things.. Any tips to share btw, I have seen your beautiful work. I will try to put it up asap. TQ.

[Dharma]

suiyuan:

Thank You for your help.

Please help me solve these questions in a non-algebraic manner.

Q1) A motorist takes 1/2 h less than the usual time to travel from KTown to JTown when he increases his average speed by 10%. For a distance of 100km, he will take 1/3 h less than the usual time if his speed is 20% more than the average speed from KTown to JTown. Find the distance between KTown and JTown.

Q2) A car travels from town P to town Q at a constant speed. When it increases its speed by 20%, the journey from P to Q takes 1 hour less than its usual time. When it travels at its usual speed for 100 km before increasing its speed by 30%, the journey also takes 1 hour less than usual. Find the distance between the two towns.

http://www.postimage.org/

[Dharma]

suiyuan:

Thank You for your help.

Please help me solve these questions in a non-algebraic manner.

Q1) A motorist takes 1/2 h less than the usual time to travel from KTown to JTown when he increases his average speed by 10%. For a distance of 100km, he will take 1/3 h less than the usual time if his speed is 20% more than the average speed from KTown to JTown. Find the distance between KTown and JTown.

Q2) A car travels from town P to town Q at a constant speed. When it increases its speed by 20%, the journey from P to Q takes 1 hour less than its usual time. When it travels at its usual speed for 100 km before increasing its speed by 30%, the journey also takes 1 hour less than usual. Find the distance between the two towns.

http://www.postimage.org/

http://www.postimage.org/

[tianzhu]

N3SKiasu:

I managed to solve the above using Model, but it is rather comple

Hi

Since you can get the answer through MD, it shows that you are probably on the right track.

Please post your MD, and I'll see if I can offer some help to simplify it.Do it, I am sure you'll gain from it.

You may insert images by following these links
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=2699&start=15
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=3767&start=30

[Dharma]

N3SKiasu:

Dear Dharma, thanks for solving my earlier question.


I have one Q :
2 groups of people, A and B are working on a project. If 18 people move from group A to group B, then group B will have 3 more people than group A. If we take away 18 people from both groups, then the remaining people in group B is 5/8 of that of group A. Find the number of people in each group at first. (Ans :106 and 73).

I managed to solve the above using Model, but it is rather complex. I wld like to seek your advice whether/how above can be solved by your usual Units/Parts method. Appreciate if you cld enlighten.

Btw, my earlier question
In a classroom, when a boy stands up, the number of boys sitting becomes 4/5 of the number of girls sitting. On the other hand, when a girl stands up, the number of girls sitting becomes 8/7 of the number of boys sitting. How many boys and girls are there in the class altogether?

Your answer contained:
3u=5p
1u = 5 & 1p=3

May I kw how is the last step being deduced from the earlier step?
Sorry if this question sound silly, I think I obviously unable to grab an impt concept here, :oops: wld appreciate your enlightenment.

Thks very much Dharma, for your help.

Hi N3SKiasu,

I'll answer your Q first.
http://www.postimage.org/

[Tang]

Dharma:

N3SKiasu:

Hi, kindly help with this question:


In a classroom, when a boy stands up, the number of boys sitting becomes 4/5 of the number of girls sitting. On the other hand, when a girl stands up, the number of girls sitting becomes 8/7 of the number of boys sitting. How many boys and girls are there in the class altogether?

Question looks similar to the Mary & Peter question but still can't figure out. :oops: pls help.

http://www.postimage.org/

Hi Uncle Dharma,
As highlighted in one of your earlier postings, we cannot solve 2 unknowns with just one equation. Hence besides equating the Total, we will need to equate the number of boys (or the number of girls) to solve the 2 unknowns. Otherwise there will be multiple answers for 1u and 1p. For your kind consideration.

[Dharma]

Hi Tang,


I've revised it
http://www.postimage.org/