Q&A - P4 Math

[tianzhu]

elisammom:

Hi

Anyone can help me solve this question?

Ms CHUA spent $1331 on 40 CDs and DVDs. Each cd cost $17 and each DVD cost $48. How many CDs did she buy?

Thanks

Hi

Besides Guess and Check, you may also use “Make A Supposition”

If all were DVD

40*48 ----- 1920

1920 – 1331 ------ 589

Difference in cost between DVD and cd ------ 48 - 17 -----31

Number of cd ------- 589/31 ------19

Best wishes

[elisammom]

Hi tianzhu


Thanks so much.
Wondering if model method can be used to solve this prob?

Thanks

[tianzhu]

elisammom:

Hi tianzhu


Thanks so much.
Wondering if model method can be used to solve this prob?

Thanks

Hi

MD is one of many problem solving heuristics in primary school maths. It’s not the only one.

Of course, students may draw some form of visual representation if they think MD might help them to see the solutions.

There were some examples in earlier posts.

Best wishes

[MathIzzzFun]

elisammom:

Hi tianzhu


Thanks so much.
Wondering if model method can be used to solve this prob?

Thanks

Hi

questions like this can also be solved using the area model ...

http://i50.tinypic.com/11izp79.jpg\">

cheers.

[elisammom]

:thankyou: All

[mmpiglet]

Hi Tianzhu,


I was looking at how you use the “Make A Supposition” method to solve a "Guess and Check" question.

I was trying to use the “Make A Supposition” method to solve the following question, but got stuck halfway through.

Bookmarks are sold at 4 for $5 and pens are sold at 3 for $4. Kenny bought an equal number of bookmarks and pens.He paid a total of $124. How many bookmarks and pens did he buy altogether ?

Can you show me how to solve using the “Make A Supposition” method ?

Thks

[tianzhu]

mmpiglet:

Hi Tianzhu,


I was looking at how you use the “Make A Supposition” method to solve a \"Guess and Check\" question.

I was trying to use the “Make A Supposition” method to solve the following question, but got stuck halfway through.

Bookmarks are sold at 4 for $5 and pens are sold at 3 for $4. Kenny bought an equal number of bookmarks and pens.He paid a total of $124. How many bookmarks and pens did he buy altogether ?

Can you show me how to solve using the “Make A Supposition” method ?

Thks

Hi

Good Afternoon.

First thing first, why do you want to consider “Make a Supposition” for this question?

I’d not use it. For questions involving “MS”, typically the total number and cost are given.

In your question, only the total cost is given.

You may use the “Grouping Concept”.

The key point to note is Kenny bought an equal number of bookmarks and pens. Bookmarks are sold in group of 4 and pens sold in group of 3.

For the pens and bookmarks to be equal in numbers, we need to start with a common multiple which is in this case 12 (3 and 4).

4 bookmarks ------ $5
12 bookmarks ------ $15 (3*5)

Likewise

3 pens ------ $4
12 pens ----- $16

Total cost for a group of 12 bookmarks and pens ------- 15+16 ------31

124/31 -------- 4

You’ve 4 groups of 12 bookmarks and pens.

48 bookmarks and 48 pens (96)

Best wishes

[mmpiglet]

Dear Tianzhu,


Thanks for showing me the method. My ds was taught MS during her tuition class and to reinforce what she had learnt, I’d picked some past year questions which look similar to the ones used for MS method. But now I realised that MS method can only be used for certain questions.

[elisammom]

Pls help this


2 boys have as many sweet as 3 girls. The total nos of sweets for 6 boys and 7 girls are 192. How many does each boy and girl has?
Thanks!

[MathIzzzFun]

elisammom:

Pls help this


2 boys have as many sweet as 3 girls. The total nos of sweets for 6 boys and 7 girls are 192. How many does each boy and girl has?
Thanks!

Hi

2 boys --> 6 units of sweets
1 boy --> 3 units of sweets

3 girls --> 6 units of sweets
1 girl --> 2 units of sweets

So, 6 boys + 7 girls --> 18 units + 14 units = 32 units of sweets
32 units of sweets --> 192
1 unit of sweets --> 6

Each boy has 18 sweets, each girl has 12 sweets

cheers.