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 By: geniuskids (offline)  Sunday, October 21 2012 @ 03:45 AM CDT (Read 777 times)
geniuskids

Q11: The ratio of the number of children to the number of adults at a party was 2:5.
After 35 children and 35 adults joined the party, the ratio of the number of children to the adults became 3:4.
How many children were there at first?

Urgent Help!

Active Member

Registered: 11/12/11
Posts: 169

 By: echeewh (offline)  Sunday, October 21 2012 @ 07:45 AM CDT
echeewh

Hi there,

Following pls find my worked solution:

<Before>
C : A
2 : 5

<After>
3 : 4

<Process>
After 35C and 35A joined the party, the difference between C and A <before> and <after> remains the same.

Apply <Unchanged Difference> concept,

Diff <Before> = 3u
Diff <after> = 1u

Multiply Diff <after> 3x will make both Diff the same.

so the new <After> ratio becomes ...

<After>
9 : 12

Comparing the <Before> and new <After> ratios, it shows an increase of 7u for both C and A.

Hence,

7u --> 35
1u --> 5

Number of C (at first) = 2u --> 2 × 5 = 10

===========

Trust this helps.

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

Cheers,
Edward

Active Member

Registered: 04/21/11
Posts: 627

 By: geniuskids (offline)  Sunday, October 21 2012 @ 08:49 AM CDT
geniuskids

Hi Edward, Thanks very much! Managed to get it!

Active Member

Registered: 11/12/11
Posts: 169

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