How many liters of a 20% solution of acid should be added to 10 liters of a 30% solution of acid to obtain a 25% solution?

Question

The answer in liters please!

Answer 1

25% is exactly in the middle between 20% and 30%

if you have 10 liters of a 30% solution you need 10 liters of a 20% solution

this is just an observation; you need to show the work and not all problems will be like this one

 

x=# of liters needed of the 20% solution

20%*x+30%*10=25%*(x+10)

0.2x+0.3*10=0.25*(x+10)

0.2x+3=0.25x+2.5

3-2.5=0.25x-0.20x

0.5=0.05x

multiply both sides by 100 (or by any smaller number that eliminates the decimals-like 20)

50=5x

x=50/5

x=10 liters of the 20% solution is needed

if you multiplied both sides by 20 you would have gotten 10=1x, or x=10