document.write( "Question 800637: How much of a 5% solution was there originally if, after 66 mgs of water evaporated, it turned into a 11% solution?\r
\n" ); document.write( "\n" ); document.write( "I can do mixture problems when you are adding but for some reason I get stuck up on these problems when you have to subtract (i.e. evaporating). \n" ); document.write( "
Algebra.Com's Answer #483179 by DrBeeee(684)\"\" \"About 
You can put this solution on YOUR website!
I'm with you! Never did evaporation, but should be the same as adding except for a minus sign lol.
\n" ); document.write( "Let s = mgm of solution (never changes)
\n" ); document.write( "Let w = initial mgm of water
\n" ); document.write( "Initially we have
\n" ); document.write( "(1) s/(s+w) = 0.05 or
\n" ); document.write( "(2) s = 0.05*(s+w) or
\n" ); document.write( "(3) s = 0.05s + 0.05w or
\n" ); document.write( "(4) s(1-0.05) = 0.05w or
\n" ); document.write( "(5) 0.95s = 0.05w or
\n" ); document.write( "(6) s = (0.05/0.95)*w or
\n" ); document.write( "(7) s = w/19
\n" ); document.write( "With enough experience solving solutions, you may have been able to write equation (6) directly from the problem statement, i.e.
\n" ); document.write( "(8) s/w = (5%/95%)
\n" ); document.write( "Now that 66 mgms of water has evaporated, the new solution has increased to 11%.
\n" ); document.write( "You may readily see how we can write
\n" ); document.write( "(8) s = (11/89)*(w-66) for the new solution. If not let's go slower.
\n" ); document.write( "We now have
\n" ); document.write( "(9) s/(s+w-66) = 0.11 or
\n" ); document.write( "(10) s = 0.11s + 0.11*(w-66) or
\n" ); document.write( "(11) 0.89s = 0.11*(w-66) or
\n" ); document.write( "(12) s = (11/89)*(w-66)
\n" ); document.write( "Since the amount of solution, s, does not change we can set (7) equal to (12) to get
\n" ); document.write( "(13) w/19 = 11/89w -11*66/89 or
\n" ); document.write( "(14) (11/89 - 1/19)*w = 11*66/89 or
\n" ); document.write( "(15) (209-89)/(89*19))*w = 11*66/89 or
\n" ); document.write( "(16) w = 11*66*19/120 or
\n" ); document.write( "(17) w = 114.95
\n" ); document.write( "Then
\n" ); document.write( "(18) s = w/19 or
\n" ); document.write( "(10) s = 6.05
\n" ); document.write( "Answer: initially there is 6.05 mgm of solution and 114.95 mgm of water.\r
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