Question 445611
the cooling system in ann's car contains 19 liters of 30% antifreeze.
 how much coolant must be drained out and replaced with 80% antifreeze so that 
the system will contain 50% antifreeze? 
:
Let x = amt of 80% antifreeze added, this is also the amt of 30% antifreeze removed
:
.30(19-x) + .80x = .50(19)
:
5.7 - .3x + .8x = 9.5
:
-.3x + .8x = 9.5 - 5.7
:
.5x = 3.8
x = {{{3.8/.5}}}
x = 7.6 liters of 80% antifreeze added, the same amt of 30% removed
:
how much of the original coolant will be left in the car?
19 - 7.6 = 11.4 liters of 30% antifreeze remain
:
:
Check solution
.3(11.4) + .8(7.6) = 9.5