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 Post subject: GMAT Percentage
PostPosted: Thu May 21, 2009 8:52 pm 

Joined: Thu May 21, 2009 8:50 pm
Posts: 2
Can you explain to me how mixing a solution with 20% hydrogen peroxide with another solution that contains .05% hydrogen peroxide and not adding any water yields 15% hydrogen peroxide?

Note that understand the math formula provided in the solution. However I don't see how not diluting any mixture will yield less hydrogen peroxide.

Thanks in advance for your help with this.

Mary Kay Richardson

 Post subject: Re: Math test 2 question
PostPosted: Mon May 25, 2009 11:19 am 
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Joined: Mon Apr 06, 2009 5:44 pm
Posts: 81
Here is how we set this problem up

We begin with 3 quarts of Minum. Since Minum is 5% HP by volume, then (5/100)(3 Qt) = 0.15 Qt HP in the Minum.

Next we have some volume, say x, of Maxim. And, Maxim is 20% HP, so (20/100)(x Qt) = 0.2x Qt HP in the Maxim.

The question asks how much of Maxim we have to add to Minum to end up with a solution that is 15% HP:

So we take the part over the whole and set it equal to the percentage:

Volume of solution that is HP / Total Volume = 15/100

[ (0.15) + (0.2)x ] / [3 + x ] = 15/100 We simply cross multiply here and solve for x. x = 6

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