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If a chemist needs 90 milliliters of a 69% solution but only has 61% and 79% solutions available, how many milliliters of each solution should be mixed together

 Feb 4, 2020
 #1
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Let the number of milliliters of  61% solution be  x

Let the number of milliliters of 79% solution be  (90- x)

 

So

 

61%  *  number of mils of this solution  +   79%  * number of mils of this solution  =  69% * 90

 

So

 

.61 * x   + .79 (90 - x)  = .69 * 90     simplify

 

.61x + 71.1 - .79x  =  62.1      

 

-.18x + 71.1  = 62.1        subtract  71.1  from both sides

 

-.18x  = -9          divide both sides by -.18

 

x = 50

 

So.....50 mils of 61% solution

 

And

 (90 -50)  = 40 mils of 79% solution

 

 

 

cool cool cool

 Feb 4, 2020

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