Amechanic needs a radiator to have 50% antifreeze solution. the radiator currently is filled with 4 gallons of 15% antifreeze solution. how much antifreeze mixture should be drained from the car if the mechanic replaces it with pure antifreeze.

let x=gallons of current mixture to be drained and replaced with pure antifreeze.
4-x=gallons of current mixture remaining in the car.

0.15(4-x)+1.00x=0.50 x 4
0.6-.15x+x=2
0.85x=1.4
x=1.4/0.85 =1.65 gal

Thus, 1.65 gallons of current mixture to be drained and replaced with pure antifreeze.

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explanation:

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answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e