Q&A - PSLE Math

[AJH]

tianzhu:

htn:

tianzhu
how to use MD to solve this q? can teach me?
TIA

Hi mumwgals and htn

MD refers to “Model Drawing” or Model Diagram”.

In this question, the units or boxes showing boys and girls in the parade ground and indoor hall are of different measures. They are not of the same sizes.

A student should note that the number of boys and girls remains the same before and after the transfer. The total number of 1000 did not change at all.

There are two unknowns with two linear equations.Recall the time at lower primary when you’re using the stars and moons, you could actually solve the equations pictorially as shown in the slide. This question is crafted in such a way that it is pretty neat to use MD.

Otherwise, students may choose to work using “Units and Parts” or letters of the alphabet as representation. Use the method you are comfortable with.

Hope this helps.

Best wishes

http://farm7.static.flickr.com/6070/6154555481_a1f43e1359_z.jpg\">

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

[jewelbox]

TianZhu, thanks for the soln on Bala's age. :thankyou:

[charsen]

[quote="jewelbox"]Hi, appreciate any help to solve these qns. Thanks.


1)In a sch hall, chairs were arranged in rows such that there were exactly 9 chairs in each row. For a concert, Mr ong brought 6 more chairs into the hall and rearragned all the chairs. Thee are now exactly 7 chairs in each row and 12 more rows than before. How many chairs are there in the sch hall for the concert? (PSLE qn)[quote]
Hi
This question has been discused in page 507.It is similar to this question.
12 new rows of 7 chairs----->84 chairs
no. of chairs removed from the original arrangement----->78 chairs
original no. of rows---->78/2=39
39x9+6=357chairs(ANS)
Cheers

[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