2011 PSLE Discussions and Strategy

[Pen88n]

Vanilla Cake:

Vanilla Cake:

Paper 2
Q13. 20 boys
Q16. (a) 54 litres (b) 20 cm

Pen88n:

There are 2 questions whereby he has different answers compared with yours and I've checked through and his answer seems ok. Below are the 2 questions:

Q13) His ans: 34 boys
Adult: Boys : Girls => 16 : 3 : 1
Diff between boys and girls: 3u - 1u = 36 => u = 18
Adult + Girls: 17u = 18 x 17 = 306
90% are adults and girls, 10% boys: 306 / 9 = 34 boys

Q16(b) His ans: 7.5cm
After 20 mins, 6l of water drained
2 container base is 500+300 cm sq, so height will be: 6l / 800 cm sq = 7.5cm

Here's are the workings done by younger sister for the above 2 questions:

Q13
Before
Adults -> 80% ie 0.8u
Boys -> 75/100x20% = 15% ie 0.15u
Girls -> u-0.8u-0.15u = 0.05u

After
Adults -> 0.8u (No change)
Girls -> 0.05u (No change)

Adults+Girls -> 0.8u+0.05u = 0.85u -> 90%
Boys -> 10% = 0.85u/90x10 = 17u/180

Difference between boys and girls in the beginning -> 0.15u-0.05u = 0.1u
0.1u -> 36
u = 360

Boys (before) - Boys (after) = 0.15u - 17u/180 = u/18 (Boys that left)
u/18 = 360/18 = 20

Number of boys that left the hall = 20

Q16(a)
800-500 = 300
(40x50x30)-(300x20) = 54000 cm3 = 54 litres
Amount of water left in the tank after 20 minutes = 54 litres

Q16 (b)
800x20 = 16000
Assume height of the water level to be u,
(ux500)+(ux300) = 16000
u = 20 cm
Height of the water level in the 2 containers after 20 minutes = 20 cm

Alternative solution for Q16 (b) done by http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=4450 is over here.

Pen88n:

Hope to share learning. Once again, thanks for sharing.

You are most welcome!

VC,
I understand your Q13 and Q16(b) and realised where my DS has gotten wrong. Thanks again.

[Vanilla Cake]

Pen88n:

Vanilla Cake,

Btw, do you happen to have the answer to MW tuition Maths paper from the unknown school? Again, DS has only attempted paper 2, and I'm looking for an easy way out for marking instead of doing all the sums again Thanks in advance.

Hi Pen88n,
As my younger sister is doing the P6 Prelim Chinese papers at this moment, I will get her to do the MW tuition Maths paper from the unknown school by tomorrow. Will post her answers for paper 2 by tomorrow's afternoon.
Thks for your understanding.

[Pen88n]

Vanilla Cake:

Vanilla Cake:

Paper 2

Q10. 49.16 kg (correct to 2 decimal places)

Pen88n:

As usual, DS only attempted paper 2. There is a question with a different answer:
Q10) His ans: 47.8kg
Total of 3 boys: 72.6kg x 3 = 217.8kg
C:B:A = 8:10:15
Carl's weight without considering defect: 8/33 x 217.8kg = 52.8kg
Consider defective: 52.8kg - 5kg = 47.8kg

Note: the defective scale is affecting the 3 boys each 5kg difference. If you minus off 15kg difference from the total, based on the ratio of the boys' weight, it will be inaccurate as it is thus not the same 5kg difference for each boy.

Q10 is a controversial question and the answer depends on how you interpret it. In fact, I have posted it over http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=4320 and hope to get some replies.

My younger sister also did the way that your DS did to get 47.8 kg.

72.6x3 = 217.8
B : A
2 : 3

B : C
5 : 4

B:A:C
10:15:8

217.8/33x8=52.8
52.8-5 = 47.8 kg (Carl's actual mass)

However, I think that the correct answer should be 49.16 kg (correct to 2 decimal places).

I've attempted to work backwards with the 2 answers, and I must say your answer is correct as it actually provides the correct ratio between A:B:C. I've not quite figure out the exact reasoning yet.......something for me to dream about tonight.

You and your sis are quite strong in your Maths foundation. Thanks for your sharing!

[Pen88n]

Vanilla Cake:

Pen88n:

Vanilla Cake,

Btw, do you happen to have the answer to MW tuition Maths paper from the unknown school? Again, DS has only attempted paper 2, and I'm looking for an easy way out for marking instead of doing all the sums again Thanks in advance.

Hi Pen88n,
As my younger sister is doing the P6 Prelim Chinese papers at this moment, I will get her to do the MW tuition Maths paper from the unknown school by tomorrow. Will post her answers for paper 2 by tomorrow's afternoon.
Thks for your understanding.

Thanks, VC. Really appreciate your help.

[Verysuperkiasu]

ngbrdad:

Correction tapes - controversial item lol
DS said they were told it's allowed but not encouraged as it may cause sheets of papers to stick together.
He and his classmates have been doing without correction tape during exams for the whole P6 so I guess I will just let it be that way.

Oh will it get stuck? Then buy the good quality one - I always look for 'quick drying' and most important will not show the erased markings after drying. Cost more but good investment.

[Verysuperkiasu]

ppnqq:

Your child had gotten this? When did your child receive this because my child and children of my friends' did not receive this at all. They need to show this before they are allowed to take the papers?

Hope it's really not been given to them yet, am worried that they may have received but lost it! :scared: :nailbite:

Yes, my son and his classmates were given the entry proofs quite a while back - can't remember when, think it's after the june hols.

[8228]

Verysuperkiasu:

ngbrdad:

Correction tapes - controversial item lol
DS said they were told it's allowed but not encouraged as it may cause sheets of papers to stick together.
He and his classmates have been doing without correction tape during exams for the whole P6 so I guess I will just let it be that way.

Oh will it get stuck? Then buy the good quality one - I always look for 'quick drying' and most important will not show the erased markings after drying. Cost more but good investment.

Which brands are good? Thanks.

[andante]

Hi all,

anyone got rulang or maha bodhi 2011 prelim maths paper ?

[ppnqq]

MandyMummy:

Hi, ppnqq, the entry proof was given to my ds sometime in July. Students are supposed to check that the information printed on the entry proof is correct and any changes had to be done by 22 July. My ds brought his entry proof for his LC but he said invigilators did not check. But I think still need to bring for every written paper leh.

Oh no, then I think they could have misplaced it or dumped it away! :yikes: :nailbite:

[MandyMummy]

ppnqq:

MandyMummy:

Hi, ppnqq, the entry proof was given to my ds sometime in July. Students are supposed to check that the information printed on the entry proof is correct and any changes had to be done by 22 July. My ds brought his entry proof for his LC but he said invigilators did not check. But I think still need to bring for every written paper leh.

Oh no, then I think they could have misplaced it or dumped it away! :yikes: :nailbite:

Quickly check to see if you can find it. If not, can ask the school to print another copy for you.