document.write( "Question 280702: How many liters of water must be added to 7 liters of a 20% acid solution to obtain a 10% acid solution? \n" ); document.write( "

Algebra.Com's Answer #204005 by oberobic(2304) $\"\"$ $\"About$

You can put this solution on YOUR website!
With solutions, you need to keep track of how much 'pure' stuff you have or need to have.
\n" ); document.write( "In this case, you don't know how much solution you will end up with. You just know that you have 7 liters of a 20% solution. 7 * .2 = 1.4 liter of pure acid.
\n" ); document.write( "You do know that you will be adding pure water, which is 0% acid.
\n" ); document.write( "And you want to cut the acid from 20% down to 10%.
\n" ); document.write( ".
\n" ); document.write( "Logically, the 10% acid solution will have 1.4 liter of pure acid = 7 liters of the 20%.
\n" ); document.write( ".
\n" ); document.write( ".1x = 1.4, where x = total volume
\n" ); document.write( ".
\n" ); document.write( "x = 14 liters
\n" ); document.write( ".
\n" ); document.write( "This suggests that if you take 7 liters of 20% acid and add 7 liters of 0% acid, you end up with 14 liters of 10% solution.
\n" ); document.write( ".
\n" ); document.write( "Logically, you have to cut the acid solution in half, so it makes sense you have to double the volume.
\n" ); document.write( ".
\n" ); document.write( "Done \n" ); document.write( "

\n" );