Q&A - PSLE Math

[Vanilla Cake]

abc_parent:

Does anyone know where to find the complete step by step solutions for SCGS Prelims. Not sure how you feel about it but I cannot do most of the questions in paper 2.

Pls post those questions in paper 2 from http://www.orlesson.org/orp/09Ma/2009-P6-Math-SA2-SCGS.pdf that you cannot do and I am sure that many people in KSP forum are willing to help you.

[Vanilla Cake]

abc_parent:

There's also much discussion about prelims 2010. May I know where I can find them and find the solutions?

Over http://psle2010a.blogspot.com/, http://www.onsponge.com/forum/35-thinkingmathonsponge.html and KSP forum.

[tianzhu]

Vanilla Cake:

Uncle Tianzhu,

There is a better method by moving around and pls assist for the drawings when you have time.

Hi VC

I am not sure if I’ve managed to capture what you meant by moving around.

When doing questions on circles, an important point to note is to try and rearrange the figures into familiar shapes.

I’ve tried to reduce the shaded areas into a familiar shape similar to that of a big eye within a 20cm square.P6 should be very comfortable with calculating the area of the big eye.

There are two ways to do it, whichever way you choose, you should get an answer of 228 sq cm.

Hope this helps.

Best wishes

http://farm5.static.flickr.com/4151/4999782779_776bdde4cb_z.jpg\">

[snowman.022851697]

Abc parent question16


http://i872.photobucket.com/albums/ab289/flightlevel350/Math%20solutions/e46d29el-bb8e-4733-8598-cd91ff91728a.jpg\">

[leesf]

Hi, appreciate if you can help on this question from Kong Hwa practice paper.


9 fewer pupils in the lower primary than upper primary signed up for the mass run this term. 2/3 of those registered were boys. 3/7 of the lower primary pupils were girls. 1/4 of the pupils in the upper primary were girls. How many boys took part in the mass run?

How to draw model on this question?

Thanks

[Vanilla Cake]

leesf:

Hi, appreciate if you can help on this question from Kong Hwa practice paper.


9 fewer pupils in the lower primary than upper primary signed up for the mass run this term. 2/3 of those registered were boys. 3/7 of the lower primary pupils were girls. 1/4 of the pupils in the upper primary were girls. How many boys took part in the mass run?

How to draw model on this question?

Thanks

While waiting for model drawing solutions, it's good for readers to know that the answer for this question is http://www.onsponge.com/forum/35-thinkingmathonsponge/4593-chanllenging-math-problem.html#4594.

[Maths Monster]

leesf:

Hi, appreciate if you can help on this question from Kong Hwa practice paper.


9 fewer pupils in the lower primary than upper primary signed up for the mass run this term. 2/3 of those registered were boys. 3/7 of the lower primary pupils were girls. 1/4 of the pupils in the upper primary were girls. How many boys took part in the mass run?

How to draw model on this question?

Thanks

let number of lower pupils be 7u

Lower : [7u]
Girls to Boys : [3u][4u]

Upper: [7u+9]
Girls to Boys: [1/4(7u+9)][3/4(7u+9)]

Total Boys = 4u + 3/4(7u+9)
Total Girls = 3u + 1/4(7u+9)

If 2/3 are boys, we can write the equation:
Number of boys = 2x Number of girls
4u + 3/4(7u+9) = 2 x (3u + 1/4(7u+9))
4u + 21/4u + 27/4 = 6u + 7/2u + 9/2
16u + 21u + 27 = 24u + 14u +18
u = 9

Number of boys = 4u + 3/4(7u+9) = 4x9 + 3/4(7x9+9) = 90

There could be a easier method, will spend some time to think about this.

[Dharma]

Vanilla Cake:

leesf:

Hi, appreciate if you can help on this question from Kong Hwa practice paper.


9 fewer pupils in the lower primary than upper primary signed up for the mass run this term. 2/3 of those registered were boys. 3/7 of the lower primary pupils were girls. 1/4 of the pupils in the upper primary were girls. How many boys took part in the mass run?

How to draw model on this question?

Thanks

While waiting for model drawing solutions, it's good for readers to know that the answer for this question is http://www.onsponge.com/forum/35-thinkingmathonsponge/4593-chanllenging-math-problem.html#4594.

Boys => 2/3
Girl => 1/3

Lower Pri
Boys : 4/7 = 4u
Girls : 3/7 = 3u

Upper Pri
Boys : ¾ = 3p
Girls : ¼ = 1p

7u + 9 = 4p -------------- ( 1 )

No. of boys = 4u + 3p
No. of girls = 3u + 1p

4u + 3p = 6u + 2p
2u = 1p
7u + 9 = 8u
1u = 9
1p = 18

No. of boys = 4u + 3p = 4(9) + 3(18 ) = 90

[tianzhu]

leesf:

Hi, appreciate if you can help on this question from Kong Hwa practice paper.


9 fewer pupils in the lower primary than upper primary signed up for the mass run this term. 2/3 of those registered were boys. 3/7 of the lower primary pupils were girls. 1/4 of the pupils in the upper primary were girls. How many boys took part in the mass run?

How to draw model on this question?

Thanks

Hi

Hope this helps.

Best wishes

http://farm5.static.flickr.com/4128/5002283329_a7d8683c3f_b.jpg\">

[leesf]

Thanks to Vanilla cake, Maths monster, Dharma & also Tianzhu for the solutions and model. This is a great site for parents like me who can’t help much on our kids’ maths problems. I would say your explanations and models is so much clearer. Thanks again for your great help.