Question

A car's cooling system of a car has a capacity of 15 liters. suppose that it is currently full of a 40% antifreeze mixture. you want 60% antifreeze mixture so you drain some of the current mixture and then add the pure antifreeze. How much antifreeze should be added?

Answer 1

you must drain the same amount as the amount you are going to add , to keep 15 L in there

let that amount be x L

so we are draining .4x L of antifreeze and then adding x L of pure antifreeze

so .4(15) - .4x + x = .6(15)
times 10
4(15) - 4x + 10x = 6(15)
60 + 6x = 90
6x = 30
x = 5

Answer 2

i don't have an answer but i have a question:

At the end of Summer, Puss discovers that his radiator antifreeze solution has dropped below the safe level. If the radiator contains 4 gallons of a 25% antifreeze solution, how many gallons of pure antifreeze must he add to bring it up to a desired 50% solution?

i am not sure how to solve this can you please put a solution to this problem