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# i need understanding how the formula came for doing this math?

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Intern
Joined: 26 Mar 2019
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i need understanding how the formula came for doing this math?  [#permalink]

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29 Mar 2019, 01:52
in 24 kg of salt water , 8% of salt . of another mixture of 4% salt. how many kg of 2nd solution must be added to the 1st mixture to get a solution that is 5% salt ?
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Re: i need understanding how the formula came for doing this math?  [#permalink]

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29 Mar 2019, 02:29
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Wasif007 wrote:
in 24 kg of salt water , 8% of salt . of another mixture of 4% salt. how many kg of 2nd solution must be added to the 1st mixture to get a solution that is 5% salt ?

This can be solved using mixtures method as depicted in the solution diagram below:
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Joined: 26 Mar 2019
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Re: i need understanding how the formula came for doing this math?  [#permalink]

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29 Mar 2019, 02:39
Thanks a lot brother....now i understand

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Joined: 30 Jan 2016
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Re: i need understanding how the formula came for doing this math?  [#permalink]

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29 Mar 2019, 10:35
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Hi Wasif007,

Welcome to gmatclub!

For theory, also check here:
Weighted Average and Mixture Problems on the GMAT
Tips and Tricks: Mixtures
ALL YOU NEED FOR QUANT ! ! !

hope this helps!
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Re: i need understanding how the formula came for doing this math?  [#permalink]

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29 Mar 2019, 11:02
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Alligator method for solving mixture problems: set it up this way:
Quantity1/Quantity2 = Percentage1/Percentage2|final percentage = (final percentage - percentage2)/(percentage1 - final percentage).

24/x = 8/4|5 = (5-4)/(8-5)=1/3 ---> 24/x = 1/3 ----> x = 72 kg
Note: Never reduce the ratio of the percentages . For example here DO NOT reduce 8/4.
If this were a multiple choice question you can eliminate any answers that are less or equal than 24 kg. why? because since the final concentration (5%) is closer to 4% than 8%, the quantity you are looking for must be greater than 24 kg.
Hope this helps
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Re: i need understanding how the formula came for doing this math?  [#permalink]

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29 Mar 2019, 11:17
Wasif007 wrote:
in 24 kg of salt water , 8% of salt . of another mixture of 4% salt. how many kg of 2nd solution must be added to the 1st mixture to get a solution that is 5% salt ?

You may find this link useful:-

https://gmatclub.com/forum/weighted-ave ... 06999.html

All the best!
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Re: i need understanding how the formula came for doing this math?   [#permalink] 29 Mar 2019, 11:17
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