How many quarts to pure antifreeze must be added to 2 quarts of a 10% antifreeze solution to obtain a 5% antifreeze solution?

Answer:

It is not possible to dilute 10% antifreeze by adding pure antifreeze

diluting a 5% mixture to a 10% mixture looks like this:

(.05*2+x)/(2+x)=.1

.1+x=.2+.1x

.1=.95x

x=.105263

so you would have to add .105 quarts of pure antifreeze to the 5% mixture in order to obtain a 10% mixture