Q&A - PSLE Math

[tianzhu]

match3frog:

- My dd always have problems with this type of questions. How to teach her to solve them?

3) A group of people met at a party. Each person shook hands with everyone else. Mr Li shook hands with 3 times as many men as women. Mrs Li shook hands with 4 times as many men as women. How many men and how many women were there at the party.

Thanks!

Hi

To make it more interesting, let’s imagine Mr and Mrs Li are hosting a party in a private room in a restaurant.

We have two scenarios here. The number of people in the room remains the same in these two scenarios.

1)When Mr Li shook hands with everyone else
2)When Mrs Li shook hands with everyone else.

If you refer to the MD, the number of women is shown by 1 unit + 1 (Mrs Li).

Besides MD, you may also use UM (Units Method) to solve this question.

So enjoy the moment and have fun.

Best wishes

http://farm8.staticflickr.com/7023/6644739703_59310c1a94_z.jpg\">

[jesschan]

Hi! Can someone please give me a copy of the answer sheet for Nanyang 2011 CA1 Maths Paper? I just ordered the exam papers and it will take another 5 days to receive them. My son has done the paper given by his friend and I hope I can mark it this weekend but too busy to do all the questions myself…

[match3frog]

Thank you kohkh, small & Tianzhu for taking time to answer the questions!

[Dazzle]

tianzhu:

match3frog:

- My dd always have problems with this type of questions. How to teach her to solve them?

3) A group of people met at a party. Each person shook hands with everyone else. Mr Li shook hands with 3 times as many men as women. Mrs Li shook hands with 4 times as many men as women. How many men and how many women were there at the party.

Thanks!

Hi

To make it more interesting, let’s imagine Mr and Mrs Li are hosting a party in a private room in a restaurant.

We have two scenarios here. The number of people in the room remains the same in these two scenarios.

1)When Mr Li shook hands with everyone else
2)When Mrs Li shook hands with everyone else.

If you refer to the MD, the number of women is shown by 1 unit + 1 (Mrs Li).

Besides MD, you may also use UM (Units Method) to solve this question.

So enjoy the moment and have fun.

Best wishes

http://farm8.staticflickr.com/7023/6644739703_59310c1a94_z.jpg\">

Hi Tianzhu,

I stumble upon this link and find it very useful. Being new, I am still trying to figure out the lingo used here. May I know what is MD? Also, will you show how to solve this using Unit Method? Thanks

[tianzhu]

Dazzle:

Hi Tianzhu,

I stumble upon this link and find it very useful. Being new, I am still trying to figure out the lingo used here. May I know what is MD? Also, will you show how to solve this using Unit Method? Thanks

Hi

MD refers to ‘Model Drawing” which is one of the many problem solving heuristics in primary maths.

In using UM, one basically uses ratios to work out the solution using a particular concept; in this case, the total number of people in the party remains the same.

Try it out first, if there is a need, I’ll post the solution at a later time.

Best wishes

[ksmama]

Hi, tianzhu, tks for reminder that can use units in equal total concept.

Soln in units method:
Case 1 mrs Li. M:W
3:1. (total 4 units)

Case2 mr Li. M:W
4:1. (total 5 units)

Since we knw total no of people shd b d same, convert the total units to the same using LCM of 4 n 5

So case 1 bcom. M:W
15:5 (prev no x 5)

Case 2. M:W
16:4 (previous no x 4)

Therefore no of men=16; women=5

[Chan09]

Sorry don’t quite understand the handshake problem and solution posted why u add 1 onto the model or take the largest of both men and women in the equal concept?

[tianzhu]

Chan09:

Sorry don't quite understand the handshake problem and solution posted why u add 1 onto the model or take the largest of both men and women in the equal concept?

Hi

We have two scenarios here. The number of people in these scenarios remains the same. That’s we are talking about the “Unchanged Total Concept” here.

1)When Mr Li shook hands with everyone else.
2)When Mrs Li shook hands with everyone else.

I’ve attempted to translate words into pictures with the new slide, hope it’s of some help to you.

If you refer to the earlier MD, the number of women is shown by 1 unit + 1 (Mrs Li).

We need to add 1 to the 1 unit (4) because 1 refers to Mrs Li.

Best wishes

http://farm8.staticflickr.com/7169/6657400139_b4cca0897a_z.jpg\">

[Dazzle]

Tianzhu and ksmama,

Thanks for solving the handshake problem.

[Dazzle]

ksmama:

Hi, tianzhu, tks for reminder that can use units in equal total concept.

Soln in units method:
Case 1 mrs Li. M:W
3:1. (total 4 units)

Case2 mr Li. M:W
4:1. (total 5 units)

Since we knw total no of people shd b d same, convert the total units to the same using LCM of 4 n 5

So case 1 bcom. M:W
15:5 (prev no x 5)

Case 2. M:W
16:4 (previous no x 4)

Therefore no of men=16; women=5

Just have a closer look, shouldn't Case 1 should be Mr Li and Case 2 is Mrs Li ?