Need help with a Ratio problem please !

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QUEENMA
Posts: 132
Joined: Fri Feb 20, 2009 3:05 pm

Need help with a Ratio problem please !

Post by QUEENMA »

The ratio of purple to yellow marbles in a bag is 5:6
The next day I add 28 more marbles to the bag. Now the ratio is 1:2 of purple to yellow.
How many purple marbles did we have at the beginning and at the end and how many total marbles do we have ?

Many thanks !
Queenma
aliportico
Posts: 888
Joined: Wed Aug 01, 2007 12:19 pm

Re: Need help with a Ratio problem please !

Post by aliportico »

What colour are the ones you are adding? All yellow? Or a mixture?
hermanmunster
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Joined: Fri Sep 15, 2006 9:51 am
Location: The Seaside

Re: Need help with a Ratio problem please !

Post by hermanmunster »

I am not sure that there is enough info in this...
rejim2
Posts: 92
Joined: Thu Mar 17, 2011 1:58 pm

Re: Need help with a Ratio problem please !

Post by rejim2 »

Given, Purple: Yellow as 5:6, assume there are a total of 11 marbles in the beginning
Adding 28 marbles more, will give a number of 11+28= 39
Now the new ratio of purple to yellow is 1:2
So, 39/(1+2) ie. 39/3=13
13 purple and 26 yellow at the end in the bag.

So, in the new lot of added 28 marbles, there had been 8 purple and 20 yellow.
Beginning - 5 purple marbles
End- 13 purple marbles.

I guess so, :o
fatbananas
Posts: 1411
Joined: Mon Mar 08, 2010 2:03 pm

Re: Need help with a Ratio problem please !

Post by fatbananas »

I worked it out exactly as Rejim2! Would be interested to have confirmation - or otherwise - that this is correct! :D

Where did you get the question from, Queenma?
Seize the day ... before it seizes you.
QUEENMA
Posts: 132
Joined: Fri Feb 20, 2009 3:05 pm

Re: Need help with a Ratio problem please !

Post by QUEENMA »

Thanks rejim2 and fatbananas.
This was from a paper of an independent school - Channing I think.
My daughter got the same answer ! I wanted to confirm it - because I thought there could be more than one answer here !

Queenma.
aliportico
Posts: 888
Joined: Wed Aug 01, 2007 12:19 pm

Re: Need help with a Ratio problem please !

Post by aliportico »

If it doesn't say which colour you add, there's more than one answer.

The scenario suggested above certainly works.

But there's also e.g.

Original ratio is 5:6
Final ratio is 1:2 which is equivalent to 5:10
Therefore 4 'parts' of yellow marbles have been added.
Therefore 1 'part' of yellow marbles = 7
Therefore you started off with 35 purple and 42 yellow, added 28 yellow to get 35 purple and 70 yellow, i.e. 105 altogether.

Or:
Start off with 20 purple and 24 yellow.
Add 4 purple and 24 yellow to give 24 purple and 48 yellow.

Think those are the only 3 possibilities. Was this a multiple choice question? If there was only one choice of answer that worked, I suppose that's ok :) But otherwise you have to make assumptions, which isn't ok.
mystery
Posts: 8927
Joined: Tue Jul 21, 2009 10:56 pm

Re: Need help with a Ratio problem please !

Post by mystery »

QUEENMA wrote:The ratio of purple to yellow marbles in a bag is 5:6
The next day I add 28 more marbles to the bag. Now the ratio is 1:2 of purple to yellow.
How many purple marbles did we have at the beginning and at the end and how many total marbles do we have ?

Many thanks !
Queenma
Did you copy out this question exactly? The language is a little odd for a maths problem in a test paper.
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