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 By: achieve_goal (offline)  Friday, February 01 2013 @ 06:35 AM CST (Read 883 times)
achieve_goal

Can you help me with this sum?

At first,the ratio of Tina's savings to Donny's savings was 7:8. After each of them spent \$20 on a toy, the ratio of Tina's savings to Donny's savings became 11:14. What was Donny's savings at first?

Regular Member

Registered: 09/14/11
Posts: 102

 By: echeewh (offline)  Friday, February 01 2013 @ 06:00 PM CST
echeewh

Hi there,

Following pls find my worked solution:

Apply <Unchanged Difference> concept (i.e. difference in savings at the end is the same as before), we have ...

<Before>
T : D Diff
7 : 8 1

<After>
T : D Diff
11 : 14 3

Since the difference is the same, we multiply <Before> ratio 3x ...

<Before>
T : D Diff
21 : 24 3

Comparing the <Before> and <after> ratios, there is a similar decrease of 10u for T and D. Hence,

10u --> 20
1u --> 2

D (savings at first) = 24u --> 24 × 2 = \$48

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

Trust this helps.

Do let me know again if this is different from your Answerkey or if there's further clarification.

Cheers,
Edward

Active Member

Registered: 04/21/11
Posts: 625

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