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Wednesday, June 28 2017 @ 02:07 AM CDT
 Forum Index >  Test Paper Related >  Primary 5 Matters
 NYPS P5 SA2 2014 Math
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By: akachan04 (offline)  Monday, October 12 2015 @ 06:17 PM CDT (Read 1453 times)  
akachan04

Hi,

I have the following question.

Arun, Belle and Chandra had a total of 240 marbles. Arun gave 25 marbles to Belle. Belle then gave 49 marbles to Chandra. Finally Chandra gave 7 marbles to Arun. In the end, they had an equal number of marbles.

a) How many marbles did Arun have at first?
b) Chandra used half of his pocket money he had at first to buy all the marbles at 30 cents each. How much was his pocket money?

Many thanks for your help.

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By: echeewh (offline)  Tuesday, October 13 2015 @ 09:30 PM CDT  
echeewh

Hey <akachan04>

Following is my worked solution :

*** - for alignment purpose

As this in an <Internal Transfer> process involving the exchange of marbles among A, B and C, we can apply <Unchanged Total> concept here. I.e. the total number of marbles <Before> and <After> remains the same.

Hence, there are 240 marbles in the end.

Given each of A, B and C had an equal number of marbles in the end, we have ...

240 ÷ 3 = 80

<After>
A = 80 ** B = 80 ** C = 80

Use and apply <Work Backwards> method, we have ...

<Before>

A = 80 ** B = 80 ** C = 80
**** - 7 ***************** + 7
************* + 49 ***** - 49
** + 25 ***** - 25
______________________________

**** 98 ***** 104 ******* 38
______________________________

(a)
Arun (A) = 98 (at first)

(b)

C = 38 (at first)

38 × 30 = 1140

Given that C used half of his pocket money to buy these marbles, we have ...

Total pocket money = 1140 × 2 = $22.80

======

Trust this helps.

Do let me know again if there's further clarification.

Cheers,
Edward

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By: akachan04 (offline)  Thursday, October 15 2015 @ 11:35 AM CDT  
akachan04

Hi Edward

Thanks again!

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