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July 5th, 2018, 12:14 AM   #1
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Why 4:7 is not the answer?

The contents of two vessels containing water and milk in the ratio 3:5 and 7:8 are mixed in the ratio 4:7. What would be the ratio of water and milk in the final mixture?

Please don't post the final answer. My doubt is: Why 4:7 is not considered as ratio of water and milk in the final mixture?
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July 5th, 2018, 02:07 AM   #2
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Why would you consider it without applying any maths to work it out?
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July 5th, 2018, 02:23 AM   #3
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That's not the way you should reply:

Quote:
Originally Posted by weirddave View Post
Why would you consider it without applying any maths to work it out?
You should reply like this:

when you take four parts of solution 1 (3:5) and seven parts of solution 2 (7: 8 ) , and you then combine the two solution

Then I will understand the question. Hope this helps!
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July 5th, 2018, 04:57 AM   #4
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Quote:
Originally Posted by Ganesh Ujwal View Post
That's not the way you should reply....
Aye, aye, Sir...

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"I want my soup lukewarm, in a blue bowl..."
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July 5th, 2018, 05:14 AM   #5
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When you take four parts of solution 1 (3:5) and seven parts of solution 2 (7: 8 ) , and you then combine the two solution
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July 5th, 2018, 07:21 AM   #6
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Ganesh, I was responding to your doubt, not the math question posed (because you did not want an answer to that).
The point I was trying to make was that I completely fail to understand why you would consider that as a possible solution without showing any reason why it might possibly be true.
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July 5th, 2018, 07:23 AM   #7
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Quote:
Originally Posted by Ganesh Ujwal View Post
The contents of two vessels containing water and milk in the ratio 3:5 and 7:8 are mixed in the ratio 4:7. What would be the ratio of water and milk in the final mixture?

Please don't post the final answer. My doubt is: Why 4:7 is not considered as ratio of water and milk in the final mixture?
4:7 is the ratio of the first mixture to the second. Because they did not have the same ratios of water and milk, that will NOT be the ratio of water and milk in the mixture.
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July 5th, 2018, 09:16 AM   #8
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Consider a simpler problem. A mixture of 3 pints water and 5 pints milk is added to an equal volume (8 pints) of water. What is the ratio of water to milk that results? Clearly, the answer isn't 1:1. Instead, the resulting mixture has 11 pints water to 5 pints milk.
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July 5th, 2018, 11:30 AM   #9
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The contents of 2 vessels containing water and milk in ratio 3:5 and 7:8 ...
a=3, b=5
c=7, d=8

....are mixed in the ratio 4:7.
u=4, v=7

What would be the ratio of water and milk in the final mixture?
r = ratio

General case formula for 2 vessels:
r = [u*a / (a+b) + v*c / (c+d)] / (u+v) = ?

EDIT: answer removed...

Last edited by Denis; July 5th, 2018 at 12:03 PM.
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July 5th, 2018, 11:50 AM   #10
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That comes far too close to posting the final answer.
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