Q&A - PSLE Math

[Muffins]

Tang:

James Ang:

P6 now learning Percentage topic, a question to share with students here;


Container A contains 250 red marbles and 200 blue marbles. Container B contains 600 red marbles and 150 blue marbles. How many red marbles and how many blue marbles must be moved from Container A to Container B such that 25% of the marbles in Container A are red and 75% of the marbles in Container B are red.

A -- 25 : 75 = 1 : 3

B -- 75 : 25 = 3 : 1

A + 3 B --> 250 + 600 = 850

3 A + B --> 200 + 150 = 350

4 A + 4 B --> 850 + 350 = 1200
1 A + 1 B --> 1200 / 4 = 300

2 B --> 850 - 300 = 550
B --> 550 / 2 = 275

2 A --> 350 - 300 = 50
A --> 50 / 2 = 25

250 - 25 = 225 red

200 - 25 x 3 = 125 blue (or 275 - 150 = 125 blue)

So move 225 red marbles and 125 blue marbles from Container A to Container B.

Thanks for the crystal clear explanation, Tang!

[verykiasu2010]

James Ang:

Tang:

[quote=\"James Ang\"]P6 now learning Percentage topic, a question to share with students here;


Container A contains 250 red marbles and 200 blue marbles. Container B contains 600 red marbles and 150 blue marbles. How many red marbles and how many blue marbles must be moved from Container A to Container B such that 25% of the marbles in Container A are red and 75% of the marbles in Container B are red.

A -- 25 : 75 = 1 : 3

B -- 75 : 25 = 3 : 1

A + 3 B --> 250 + 600 = 850

3 A + B --> 200 + 150 = 350

4 A + 4 B --> 850 + 350 = 1200
1 A + 1 B --> 1200 / 4 = 300

2 B --> 850 - 300 = 550
B --> 550 / 2 = 275

2 A --> 350 - 300 = 50
A --> 50 / 2 = 25

250 - 25 = 225 red

200 - 25 x 3 = 125 blue (or 275 - 150 = 125 blue)

So move 225 red marbles and 125 blue marbles from Container A to Container B.

It is correct and this sum is best solved as simultaneous equation as Tang has so brilliantly done so. :D[/quote]How many marks is this question ? the kid got it done in one minute

[Vanilla Cake]

verykiasu2010:

James Ang:

[quote=\"Tang\"]
A -- 25 : 75 = 1 : 3

B -- 75 : 25 = 3 : 1

A + 3 B --> 250 + 600 = 850

3 A + B --> 200 + 150 = 350

4 A + 4 B --> 850 + 350 = 1200
1 A + 1 B --> 1200 / 4 = 300

2 B --> 850 - 300 = 550
B --> 550 / 2 = 275

2 A --> 350 - 300 = 50
A --> 50 / 2 = 25

250 - 25 = 225 red

200 - 25 x 3 = 125 blue (or 275 - 150 = 125 blue)

So move 225 red marbles and 125 blue marbles from Container A to Container B.

It is correct and this sum is best solved as simultaneous equation as Tang has so brilliantly done so.

How many marks is this question ? the kid got it done in one minute[/quote]Hi verykiasu2010,
This is a 5-mark question from Raffles Girls' Primary School Semestral Assessment 1 2009 Paper 2 Q18 which was set on 12 May 2009.
There is only one blank space for the answer in the question paper itself so the correct answer is the total number of red and blue marbles which is 350.

Pls comment on whether the setter is looking for the correct answer as the total number of marbles to be moved or the breakdown of the red and blue marbles to be moved?
And is simultaneous equation taught at P6 level?
Are there other methods other than using simultaneous equation to solve this problem sum?

[Tang]

Vanilla Cake:

verykiasu2010:

[quote=\"James Ang\"]
It is correct and this sum is best solved as simultaneous equation as Tang has so brilliantly done so.

How many marks is this question ? the kid got it done in one minute

Hi verykiasu2010,
This is a 5-mark question from Raffles Girls' Primary School Semestral Assessment 1 2009 Paper 2 Q18 which was set on 12 May 2009.
There is only one blank space for the answer in the question paper itself so the correct answer is the total number of red and blue marbles which is 350.

Pls comment on whether the setter is looking for the correct answer as the total number of marbles to be moved or the breakdown of the red and blue marbles to be moved?
And is simultaneous equation taught at P6 level?
Are there other methods other than using simultaneous equation to solve this problem sum?[/quote]Hi Vanilla Cake,

The original question is \"How many red and blue marbles must be moved ...\"

A + 3 B = 850
3 A + B = 350
Find the value of A and B.

The above simplified question can be found in many P4 and P5 Maths Exam papers.

You may want to share with the Readers how you would normally solve such questions. Thanks.

[CoffeeCat]

Yea inany case solving the simplified simultaneous equation is similar to

using models to represent And solve

[Vanilla Cake]

Tang:

Hi Vanilla Cake,


The original question is \"How many red and blue marbles must be moved ...\"

A + 3 B = 850
3 A + B = 350
Find the value of A and B.

The above simplified question can be found in many P4 and P5 Maths Exam papers.

You may want to share with the Readers how you would normally solve such questions. Thanks.

Hi Tang,
Thanks for your reply and highlight. This question posted by James Ang is slightly different from the one in the RGPS's paper as the RGPS's question is \"How many red and blue marbles must be moved from Container A to Container B.........\" and James Ang's question is \"How many red marbles and how many blue marbles must be moved from Container A to Container B.............\"

I leave this question to Mathsguru to provide the solution. Your solution is excellent and I have printed it for my younger sister who is taking PSLE 2011 to study and learn from you. :love:

[verykiasu2010]

Vanilla Cake:

Hi verykiasu2010,

This is a 5-mark question from Raffles Girls' Primary School Semestral Assessment 1 2009 Paper 2 Q18 which was set on 12 May 2009.
There is only one blank space for the answer in the question paper itself so the correct answer is the total number of red and blue marbles which is 350.

Pls comment on whether the setter is looking for the correct answer as the total number of marbles to be moved or the breakdown of the red and blue marbles to be moved?
And is simultaneous equation taught at P6 level?
Are there other methods other than using simultaneous equation to solve this problem sum?

if it is a 5 marks qn,then expect to show all the steps and how many red and how many blue to be moved

marks are awarded for steps, method, and correct answer

[tianzhu]

Hi


When there is a problem, there are alternatives. It’s always good to look at a problem from different angles. Students may find these websites useful.

http://prischoolmaths.blogspot.com/
http://psle2010a.blogspot.com/

Best wishes

[Herbie]

Can someone help to provide the solution for the qn below:


Helen ate 50g of rice. If Helen share decreased by 12 g. Ada’s share increased by 6%. How much do they eat in total?

Tq

[Dharma]

Herbie:

Can someone help to provide the solution for the qn below:


Helen ate 50g of rice. If Helen share decreased by 12 g. Ada's share increased by 6%. How much do they eat in total?

Tq

6% - 12g
2% - 4g
100% - 200g
Ada ate 200g

Helen and Ada ate (50 + 200 = 250)g in total