Q&A - PSLE Math

[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

[tianzhu]

jewelbox:

2. Chairs are arranged in rows in a sch hall. There are 6 chairs left over if 13 chairs are put in each row. Hwoever, if 15 chairs are arranged in each row, there will be a shortage of 4 chairs. if the no. of people attending the concert is betw 200 and 30, find the no. of chairs in the hall.

Hi

Use “SL” to get the answer of 266.

Do a tabulated list of multiples of 13 + 6 and multiples of 15 – 4.

Or alternatively find the multiples of 13 and 15 which give a difference of 10.

Then find multiple of 13 + 6 or multiple of 15 – 4.

Best wishes

[tianzhu]

ximinful:

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

Hi

If you’re referring to the Speed question, I’ll try to do some sketch and PM to you early next week.

Best wishes

[Michaelia0816]

Thanks you Thank you!

[brastilava]

Hi, please help in these 2 questions:


1) 7 rows of soldiers with 20 soldiers in each row were assembled on a parade square. The soldiers were spaced out equally to form the perimeter of the parade square. The number of soldiers on the length of the parade square was twice the number of soldiers on its breadth. How many soldiers were on each side of the rectangle?

2) I am a 2-digit number. I am a multiple of 4. When I am divided by 9, there will be a remainder of 6. When I am divided by 7, there will be a remainder of 5. Who am I?

[ximinful]

tianzhu:

ximinful:

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

Hi

If you’re referring to the Speed question, I’ll try to do some sketch and PM to you early next week.

Best wishes

:rahrah: :thankyou:

[tianzhu]

brastilava:

Hi, please help in these 2 questions:


1) 7 rows of soldiers with 20 soldiers in each row were assembled on a parade square. The soldiers were spaced out equally to form the perimeter of the parade square. The number of soldiers on the length of the parade square was twice the number of soldiers on its breadth. How many soldiers were on each side of the rectangle?

2) I am a 2-digit number. I am a multiple of 4. When I am divided by 9, there will be a remainder of 6. When I am divided by 7, there will be a remainder of 5. Who am I?

Hi

Good Morning.

For Q1, please refer to this similar question.

The answers to your question are 48 and 24.

7*20 ------ 140

140 + 4 ------144

6 units ------ 144

You may carry on from here.

For Q2, use “Systematic Listing”

It may be a bit tedious, but this is the sort of durian bao chiak type of questions if students are careful in their calculations. All one needs to do is to list down the multiples and make appropriate adjustment.

The answer is 96.

Best wishes

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