# Word Problem

## Main Question or Discussion Point

Ive got an assignment of word problems and cant seem to figure this one out:

A 6 Litre car radiator is 2 thirds full of water. How much of a 90% antifreeze solution (90% is alcohol by volume) must be added to it to make a 10% antifreeze solution in the radiator?

I came up with the equation: 0.9x=(0.1)(6)

but that didnt work so any help about what the way to set up the problem would be great.

Office_Shredder
Staff Emeritus
Gold Member
First, this should probably be in the homework section, but oh well

Second, you hvae to ask yourself a different question (which you don't seem to have taken into account)

How much water is in the radiator?

4L of water

Office_Shredder
Staff Emeritus
Gold Member
Ok, this whole posting in two places isn't going to cut it, so I'm just going to stick with this thread.

If the anti-freeze solution is 90% antifreeze, then when you add a volume V of solution to a volume v of liquid, your total volume becomes V + v, and your anti-freeze portion is .9V. So how can this be applied to the problem?

ah

so the equation should be 4+.9V=6(.1)?

is that correct?

ok i tried that equation and got an answer of -3.77777 so that cant be the correct answer, so i am kind of stumped as to what to try next lol.

Office_Shredder
Staff Emeritus
Gold Member
You have to explain WHY you think that's the equation. I don't know why you think there should be a 6 at all, for example, so it's difficult to help you

HallsofIvy