Q&A - PSLE Math

Academic support for Primary 6 and PSLE
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lizawa
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Post by lizawa » Mon Oct 06, 2008 2:04 pm

heutistmeintag wrote:oh i see, now I can solve by alegbra.

B=20+G

1/3G+1/4B=19
4G+3B=19*12=228
4G+3*(20+G)=228
4G+60+3G=228
7G=228-60
7G=168
G=24
B=20+24=44
Total number of children invited is (24+44)=68

ok, can someone explain using modelling? :)
Solve by model :
--------------------
Boys : 12u + 20
Girls : 12u

1/4 boys did not come -> 3u + 5 (you can break 20 into 4 parts, each part is 5)
1/3 girls did not come -> 4u

7u + 5 = 19
1u = 2
Altogether -> 24u + 20 = 48+20 = 68.

kiasuson
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Post by kiasuson » Mon Oct 06, 2008 2:23 pm

Anymore interesting questions that were feedback from the children? My son said the paper was ok as expected..

raysusan
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Post by raysusan » Mon Oct 06, 2008 11:32 pm

lizawa wrote:
heutistmeintag wrote:oh i see, now I can solve by alegbra.

B=20+G

1/3G+1/4B=19
4G+3B=19*12=228
4G+3*(20+G)=228
4G+60+3G=228
7G=228-60
7G=168
G=24
B=20+24=44
Total number of children invited is (24+44)=68

ok, can someone explain using modelling? :)
Solve by model :
--------------------
Boys : 12u + 20
Girls : 12u

1/4 boys did not come -> 3u + 5 (you can break 20 into 4 parts, each part is 5)
1/3 girls did not come -> 4u

7u + 5 = 19
1u = 2
Altogether -> 24u + 20 = 48+20 = 68.
is this the Q47?

lizawa
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Post by lizawa » Tue Oct 07, 2008 8:09 am

raysusan wrote:
lizawa wrote:
heutistmeintag wrote:oh i see, now I can solve by alegbra.

B=20+G

1/3G+1/4B=19
4G+3B=19*12=228
4G+3*(20+G)=228
4G+60+3G=228
7G=228-60
7G=168
G=24
B=20+24=44
Total number of children invited is (24+44)=68

ok, can someone explain using modelling? :)
Solve by model :
--------------------
Boys : 12u + 20
Girls : 12u

1/4 boys did not come -> 3u + 5 (you can break 20 into 4 parts, each part is 5)
1/3 girls did not come -> 4u

7u + 5 = 19
1u = 2
Altogether -> 24u + 20 = 48+20 = 68.
is this the Q47?
Hi raysusan,

I don't think so. Q47 should be a 5-mark question. This doesn't look like a 5-mark question to me.

kiasuson
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Post by kiasuson » Tue Oct 07, 2008 9:12 am

According to my son, Q47 is about speed and the above discussed question is the last question of the paper and it is 5 marks. Anyway, same situation as lizawa... We will not want to probe our son about something that is over and done...They still have another 2 or 3 papers to go...


Priskhipo
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Post by Priskhipo » Tue Oct 07, 2008 9:40 am

lizawa wrote:
raysusan wrote:
lizawa wrote: Solve by model :
--------------------
Boys : 12u + 20
Girls : 12u

1/4 boys did not come -> 3u + 5 (you can break 20 into 4 parts, each part is 5)
1/3 girls did not come -> 4u

7u + 5 = 19
1u = 2
Altogether -> 24u + 20 = 48+20 = 68.
is this the Q47?
Hi raysusan,

I don't think so. Q47 should be a 5-mark question. This doesn't look like a 5-mark question to me.
Hi All,
This question is the last one and it is 4 marks.

kiasuson
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Post by kiasuson » Tue Oct 07, 2008 10:04 am

Those interested to know more on PSLE can read this forum.

http://forum.channelnewsasia.com/viewtopic.php?t=183752

cutemum
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Post by cutemum » Mon Oct 13, 2008 1:17 pm

can anyone help me?

Three girls, Anna, Beatrice and Calista shared a roll of ribbons. Anna's share was 1/4 of the total length of Beatrice's and Calista's ribbon. Beatrice's share was 2/3 of the total length of Anna's and Calista's ribbon. If Anna's share of ribbons is 45 cm less than beatrice's share, what is the total length of the roll of ribbons?.

lizawa
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Post by lizawa » Mon Oct 13, 2008 1:56 pm

cutemum wrote:can anyone help me?

Three girls, Anna, Beatrice and Calista shared a roll of ribbons. Anna's share was 1/4 of the total length of Beatrice's and Calista's ribbon. Beatrice's share was 2/3 of the total length of Anna's and Calista's ribbon. If Anna's share of ribbons is 45 cm less than beatrice's share, what is the total length of the roll of ribbons?.
A : B+C
= 1:4

B: A+C
= 2: 3

Note that the total no. of units in both cases are equal, ie 5 units. So the size of unit in each case is the same.

A: B
= 1:2
Since A has 45cm less than B,
1 unit = 45 cm
5 units = 45 *5 = 225 cm

Total length = 225cm.

cutemum
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Post by cutemum » Mon Oct 13, 2008 2:04 pm

yeah, that's the answer, thank you so much lizawa....

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