Q&A - PSLE Math

[ximinful]

Hi,can someone help me with nanyang 2012 prelim q10?

Ps. I know this qns has been discussed before but I don’t understand the solution.
Tia

[whitety]

tianzhu:

whitety:

Hi, need help on this qn.


Lina bought some chocolate and vanilla muffins in the ratio 2:3. She packed the chocolate muffins into boxes of 3 and the vanilla muffins into boxes of 4. There were 6 more boxes of vanilla muffins than chocolate muffins. How many chocolate muffins did Lina buy?

Thanks!

Hi

2:3 ------- 24:36

This is equivalent to 8 boxes of chocolate muffins and 9 boxes of vanilla muffins.

We are looking for 6 more boxes of vanilla muffins.

Hence multiply by 6 to get 48 of chocolate muffins and 54 boxes of vanilla muffins.

Number of chocolate muffins ---------- 48*3 ------ 144

Best wishes

Hi tianzhu,
Thank you very much !!!

[Dazzle]

Tianzhu,

Thank you so much for your answer to Q9 of MGS Prelim 2012. Will you show how to solve with Model? Thanks again.

[balu_priya]

I suggest you post this in q and a Maths.Mods please merge.

[AJH]

Hi - nd help with this question:


Mr Lee packed some oranges into big boxes and apples into small boxes. Each big box contained 50 oranges and each small box contained 30 apples. After packing, there were 12 more big boxes than small boxes. Given that there were 1240 fewer apples than oranges, how many oranges were there? ( ans: 2200 )

Thank you.

[jewelbox]

Charsen, thanks for the soln on chairs in sch halls. :thankyou:

[rsorchid]

Thanks so much.

tianzhu:

rsorchid:

Pls help, Thanks.

A florist had some roses, tulips and carnations. After selling some of them, there were 6 tulips for every 5 roses and 7 roses for every 3 carnations. After selling 168 roses, she had 456 tulips and carnations left. The number of tulips sold was the same as the number of carnations sold.
a) How many roses had she at first?
b) If the number of tulips was twice the number of carnations at first, what is the total number of tulips and carnations sold?

Hi

A neat way is to use MD.

T:R ------ 6:5 -------42:35

R:C ------ 7:3 -------- 35:15

Since the share for roses is repeated, make it the same for both set of ratios

15 + 42 ------ 57

57 units -------- 456

1 unit ------- 8

(a)Number of roses left ------- 35*8 -------- 280

Number of roses@first -------- 280+168 -------- 448

(b) Draw 1 box to show number of tulips/carnation sold.

Number of tulips left ------- 42*8 -------- 336

Number of carnations left -------- 120

1 box + 336 ------- 1 box + 120 = 1 box + 120

1 box ------- 96

The total number of tulips and carnations sold ------- 96*2 ------- 192

Best wishes

[tianzhu]

AJH:

Hi - how did u get 480? I got 460. Thank u.

Hi

This question is crafted in such a way that it’s neat to use MD.

You may also use Units and Parts or letters of the alphabet to show the variables.

What you are seeing now is already the MD.The boxes are labelled with units and parts to enable students using the UP to see better.

The number “480” refers to the number of girls.

Best wishes

[tianzhu]

Dazzle:

Tianzhu,

Thank you so much for your answer to Q9 of MGS Prelim 2012. Will you show how to solve with Model? Thanks again.

Hi

MD is one of many heuristics in the syllabus. It’s not the only way.

Sometimes, alternative way may be more appropriate.

The UP way is rather mechanical and not too difficult to pick up.

If you want to see the MD, I’ll find some time to draw and PM to you next week.

Best wishes

[tianzhu]

AJH:

Hi - nd help with this question:


Mr Lee packed some oranges into big boxes and apples into small boxes. Each big box contained 50 oranges and each small box contained 30 apples. After packing, there were 12 more big boxes than small boxes. Given that there were 1240 fewer apples than oranges, how many oranges were there? ( ans: 2200 )

Thank you.

Hi

You may use MD or work with units.

Draw three boxes (stacked up) to show the number of apples.

12*50 ------ 600

Draw five boxes to show the number of oranges. To make the MD look neater, divide 600/5 to give 120, add a bar showing 120 to each of the box.

5 boxes + 600 ------- 3 boxes + 1240

2 boxes ------- 640

1box ------ 320

Number of apples ------- 2200

Best wishes