Q&A - PSLE Math

[tianzhu]

Hi


Hope this helps.

Other than the Units Method, you may also use MD to show the flow of events.

Best wishes.

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[Brenda10]

tianzhu:

Hi


Hope this helps.

Other than the Units Method, you may also use MD to show the flow of events.

Best wishes.

http://farm6.static.flickr.com/5248/5301831898_a925296513_b.jpg\">

Thank you Tianzhu for sharing. We appreicate your valuable time to do it so wonderful.

[Brenda10]

Deleted. Double post.

[Vanilla Cake]

Belle2011:

It takes 3 men 4 days to paint 3 houses. How long does it take 4 men to paint 9 houses?

Pls refer to http://www.wecaretuition.com/studentresources/academics/Maths/downloads/Heuristics%20and%20model%20%20approach%20to%20solve%20challenging%20NewMaths%20problems%20%5BRead-Only%5D.pdf - Strategy 8: Total Amount (Quantity) of Work Rule to understand the concept to solve this type of question.

[Belle2011]

Dear tianzhu,

Thank-you for spending your precious time to share solutions.
Cheers,
Belle.

[Dharma]

Belle2011:

Another tricky question:

It takes 3 men 4 days to paint 3 houses. How long does it take 4 men to paint 9 houses?
Thank-you.

3 men can paint 3 houses in 4 days
1 man can paint 3 houses in 12 days
1 man can paint 9 houses in 36 days
4 men can paint 9 houses in 9 days

[tianzhu]

Hi


This is a question on Compound Proportion.

I think it’s covered in secondary Maths. You may wish to check with the school teacher if it is in the syllabus.

The trick to solve such question is to tackle one variable at a time.

One way to look at it.

3 men took 4 days to paint 3 houses.
1 man took 4 days to paint 3/3 or 1 house.
4 men took 1 day to paint 1 house.
4 men took 9 days to paint 9 houses.

Best wishes

[tianzhu]

Hi Brenda10 and Belle2011


You’re welcome.

Best wishes

[Lynn2]

Hi Brenda10,


That is an interesting way to solve the math prob.do u mind sharing with me the name of the book too?thanks

Lynn2

Belle2011:

Brenda10:

Hi Tianzhu

DD learn from one of the book that we got. This book has similar example to the question we encountered. Its come with model but by following the example she did not draw the model. Have PM for you.

Thank you

Dear Brenda10,
Can you share the same of this book?
I cannot solve these problems at all. Maybe my IQ is just too low. I often cannot handle the last few (4 or 5 marks) questions.
Thank-you.
Cheers,
Belle.

[Hifive]

Hi


Source : Andrew Er’s New Syllabus Mathematics

A class has a total of 40 pupils. Each girl has an average mass of 40kg and each boy has an average mass of 48kg. If the total mass of the girls is 512 kg lighter than the total mass of the boys, how many girls are there in the class ?

Ans: 16 girls.

Though the book provided the solution to the question but don’t quite get it and hope that parents/students here can provide alternative method of solution.

Thanks & Regards