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Sunday, October 22 2017 @ 05:49 PM CDT
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  CHIJ P6 SA2 (Prelim) 2009 Maths Paper 2 - Qn 17
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By: olh88 (offline)  Monday, September 13 2010 @ 02:09 AM CDT (Read 1640 times)  
olh88

Hi,

Have been teaching my kid using prelim papers from other schoolds downloaded from this website. One question (Qn. 17) from the CHIJ P6 SA2 (Prelim) 2009 Maths Paper 2 may have error, the answer key does not have workings, only answer was given but even the answer does not make sense (to me). Thought I will post in this forum if anyone has the solution or knows the problem to the question, thanks:

At carpark P the number of lorries to that of vans was in ratio 3:7
At carpark Q the number of lorries to that of vans was in ratio 8:9
When 40% more lorries from an industrial park entered carpark P and 20% of vans at carpark Q moved to carpark P, there were 76 fewer lorries at carpark P than at carpark Q.
How many vehicles were there altogether at the 2 carparks finally?

(Answer given: 564)

Thanks.

Rgds,
Ong

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By: rathanackumr (offline)  Monday, September 13 2010 @ 03:30 AM CDT  
rathanackumr


Hi olh88, the solution


Carpark P Carpark Q
Lorries : Vans Lorries: Vans
3 : 7 8 : 9
= 15 : 35 <-(multiply by 5)->40 : 45

15u X 40% = 6u

add to 6u(40%) to15u = 21u => new unit of lorries in Carpark P

40u - 21u = 19u which is 76
1u = 76/19 = 4
Total units 21u + 35u + 40u + 45u = 141u
4 X 141 = 564

Probably this was a modified version of the original. In this question the 20% van transfer is redundant. Moving vans from one carpark to another will not make any changes to the total no of vehicles.They are asking for the total no of vehicles altogether. I believe there was a 1st part where the question asked for the no. of vans at carpark P. The setter omitted the question but forgot to remove the 20% van transfer.

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By: olh88 (offline)  Monday, September 13 2010 @ 11:06 PM CDT  
olh88

Thanks 'rathanackumr', I also worked until 21u and (40-21)u but dunno what's wrong with me did not get to the 19u = 76 part, thanks for the solution still, appreciate your help!

Ong

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