Q&A - PSLE Math

[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 ?

[match3frog]

Regarding the handshake problem - I’m just wondering, what if the student thinks that Mr & Mrs Li don’t shake hands with each other because they already know each other. Wouldn’t the answer be different?

[MathIzzzFun]

match3frog:

Regarding the handshake problem - I'm just wondering, what if the student thinks that Mr & Mrs Li don't shake hands with each other because they already know each other. Wouldn't the answer be different?

Hi

the answer will be different, but the question says : \"A group of people met at a party. Each person shook hands with everyone else.\" so regardless of whether anyone knows someone else at the party, it will have to be taken that each will shake hands with everyone else.

cheers.

[match3frog]

Hi mathizzzfun, good morning and thanks for your reply. I have to read the questions carefully


Hi ksmama, thanks for posting the solutions using units method!