SOLUTION: The cooling system of a car has a capacity of 15 liters. If the system currently has a mixture of 40% antifreeze how much of this mixture should be drained and replaced with pure

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Question 159080This question is from textbook Intermediate Algebra
: The cooling system of a car has a capacity of 15 liters. If the system currently has a mixture of 40% antifreeze how much of this mixture should be drained and replaced with pure antifreeze so that the system is filled with 50% antifreeze?
I think that the answer is 1.5 liters. I just don't know how to get it in an Algebraic expression. I used the equation 15(.5)=15(.4)+ a
Let a=the amount of antifreeze to be added. In case you couldn't tell I am severely confused.

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This question is from textbook Intermediate Algebra

Answer by jojo14344(1513) (Show Source):
You can put this solution on YOUR website!
*See this one, thank you.
Let , amount in Liters to be drained
, amount of 100% A/F to be added
Therefore,
------> working eqn
The above eqn means the 15L capacity with 40% A/F is drained with liters amount with the same mixture of %40 A/F of course.Then you're adding 100% A/F in liters amount that will result to the same capacity of 15L with 50% A/F
Also, take note:

The cooling system 15L has taken out amount plus amount equals the same capacity of 15L
.
Continuing,

---> substitute in working eqn:

--------> amount to be drained = amount to be added
In doubt? go back working eqn:

thank you,
Jojo