Example 1
A radiator's capacity is 16 gallons. If the radiator is full of a 40% antifreeze solution, how many gallons must be drained and replaced with a 75% solution to obtain a full radiator of 45% antifreeze solution?
A diagram is helpful here (see Figure 1).
So 
, or 
gallons must be drained and replaced.
A diagram of the problem posed in Example
.
