<PRE><B>Question 44886</B>
How many liters (L) of a 10% silver iodide solution must be mixed with 7 L of a 4% silver iodide solution to get a 6% solution? 

Start: 7L of 4% solution has 0.04(7)=0.28 liters of active ingredient

Add: x liters of 10% solution which has 0.10x liters of active ingredient

End up with: x+7 liters of 6% solution which has 0.06(x+7) liters of active 
ingredient.

EQUATION:
active + active = active
0.28 + 0.10x=0.06x+0.42

Multiply thru by 100 to get:
28 +10x = 6x + 42
4x = 14
x=7/2= 3.5 liters (amount of 10% solution you need to add)

Cheers,
Stan H.</PRE>