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 By: zinmkw (offline)  Monday, April 30 2012 @ 10:09 AM CDT (Read 1613 times)
zinmkw

Catholic high school exam paper no43
Randy and Kelly have the same number of books at first. After Randy gave away 25 books to Kelly, Randy has 3/8 as many books as Kelly. How many books did each of them have at first?

Ans:
10/2=5
1u=25/5=5
6*5=30
30+25=55

Pls help me to explain how to get this ans: thank u

Newbie

Registered: 10/11/10
Posts: 7

 By: echeewh (offline)  Monday, April 30 2012 @ 08:35 PM CDT
echeewh

hey there,

sometimes it can be rather 'tricky' to look at the solution given in the answerkey without much explanation. Anyway, heres my worked solution for u .....
(note : *** - used to buffer up whitespace )

Use Before and After model technique...

<before>

R |----------------|
K |----------------|

<After>

**************25
***<--3u--><----
R |----------|-----|

K |----------------|-----|
**<----------8u------->
*****************----->
******************25

Using Gap & Diff technique, we have ....

8u - 3u ---> 25 + 25
5u ---> 50
1u ---> 10

R (at first ) = 3u + 25 ---> ( 3 x 10 ) + 25 = 30 + 25 = 55

==================================================

Do let me know again should there be further clarification.

Cheers
Edward

Active Member

Registered: 04/21/11
Posts: 627

 By: sokechan (offline)  Monday, April 30 2012 @ 11:08 PM CDT
sokechan

Total units -> 8+3=11u
11u / 2 = 5.5u
5.5u - original u (3u) = 2.5u
8u - 5.5u = 2.5u
2.5u -> 25
5.5u -> 55

Junior

Registered: 02/25/11
Posts: 23

 By: zinmkw (offline)  Tuesday, May 01 2012 @ 08:11 AM CDT
zinmkw

Thanks a lot for the explaniation

Newbie

Registered: 10/11/10
Posts: 7

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