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 2011 SA1 ACS Maths Paper 2 Q16
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By: geniuskids (offline)  Sunday, May 06 2012 @ 11:01 PM CDT (Read 1857 times)  
geniuskids

Its a question on "MARBLES". How can marbles be split. Answers given is 62.5. Strange????

(16) There are some crystal and glass marbles ina pouch. If 3 crystal marbles are removed from the pouch, the number of crystal marbles will be 1/6 of the glass marbles left. If 5 glass marbles are removed from the pouch, the number of crystal marbles left will be 1/4 of the glass marbles left. How many marbles are there in the pouch at first?

Can somebody explain please>

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By: echeewh (offline)  Monday, May 07 2012 @ 05:52 AM CDT  
echeewh

hi there,
another person here posted same question earlier and I asked specifically for the answerkey as no details or whatsoever were given by the person ( as in which past year paper , etc). While working on the solution, I noticed that it wont be a whole number answer and i stopped midway prompting me to ask for the answerkey. Although the answerkey is not realistic or doesnt seemed logical, mathematically that answer of 62.5 fits into the question correctly. As we are not the setters, I think the proportions ( fractions ) or the numbers given in the question may not be very appropriate ( juz a personal opinion ).

btw, strangely enough, the Nanyang Paper 2 Q15 that I got has the diagram to work on. Will post this to you later....

As for the RGPS Paper 2 Q9, you will find it crystal clear if you know how to use the Branching method.. Smile

Cheers,
Edward

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By: khengsin (offline)  Wednesday, May 09 2012 @ 04:50 AM CDT  
khengsin

I seem to be able to get whole number answer for this question .. please comment on the following:

<before>
C : 1p + 3
G : 5p

<after>
C : 1u
G : 3u + 5

1p + 3 --> 1u , 1p --> 1u -3 , 3p --> 3u - 9 ...(1)
5p --> 3u + 5 ...(2)

(2) - (1) , 2p --> 14
1p --> 7

Before there are 6p + 3 , therefore 6x7 + 3 = 45 marbles in the pouch.
Ans = 45 marbles

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By: echeewh (offline)  Thursday, May 10 2012 @ 12:23 AM CDT  
echeewh

Hey KhengSin,,

The question stated "If 3 crystal marbles are removed from the pouch, the number of crystal marbles will be 1/6 of the glass marbles left".

Your model shows
<before>
C : 1p + 3
G : 5p

This < G : 5p > is incorrect; it should be showing 6p instead based on the statement above.

Best regards,
Edward

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By: khengsin (offline)  Thursday, May 10 2012 @ 12:38 AM CDT  
khengsin

Hi, to reply you..

In this question , it is stated as fraction 1/6 and not ratio 1:6 ... so the total parts or units is still 6. So 1p for crystal and 5p for glass marbles as in the ratio 1:5.

Hope this clarify the question.

Brgds/Khengsin

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By: khengsin (offline)  Thursday, May 10 2012 @ 12:47 AM CDT  
khengsin

Hi Edward..

Yes you are right... my mistake in interpreting the question..

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