# Water density and temperature

#### jazzchan

Dear all

Here is a question i need to help

Can I know how much water at 25^C to put into a water at 75^C and then the mixture is 60^C ??

thanks and best regards

Jazz

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#### VietDao29

Homework Helper
Use
$$Q = mc\Delta t$$
Viet Dao,

#### jazzchan

is it mean the Q of temperature from 75 to 60^c is equal to the Q of 25 to 60^C ??

thank

#### HallsofIvy

Homework Helper
Since we are dealing with water of a constant heat capacity, it's not the complicated. You can treat it as a "mixture" problem. If you have x cm 3 of 25 degree water, the heat is proportional to 25x. If you have y cm3 of 75 degree water, the heat is proportional to 75y. Mixing those together you have x+ y cm3 of water that you want to be 60 degrees so the mixture's hear is proportional to 60(x+y). You want 25x+ 75y= 60(x+y). Of course, that's one equation in two unknowns because you didn't say how much of the 25 degree water you had or how much water you wanted to end up with.

#### jazzchan

yes...my question is to find how much 25 degree water should be used...

would u tell me more ??

thanks...

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