Can someone PLEASE help me with my problem? A solution contains 6% salt. How much water should be added to 70 ounces of this solution to make a 4.2% solution? Help me solve this please!

Question

anonymous · Answer

Is the answer 105 by any chance?

anonymous · Answer

(.06)(70oz) = (.042)(x)
Concentration problem

anonymous · Answer

Let's put it into an equation:
We have that, at 70 ounces, such contains 6% salt. As we increase the amount of water $v$, the percentage of salt $m$ decreases directly, so:
$$
vm=c
$$For some constant $c$. We find this constant to be:
$$
70\cdot0.06=4.2=c\implies\
vm=4.2
$$We need $m=0.042$:
$$
0.042v=4.2\implies\
v=100
$$By this, we must add $100-70=30$ ounces to lower the concentration to 4.2%.

anonymous · Answer

you will then need to subtract the 70 from your new total to get water added.

anonymous · Answer

So like lolwolf said 100 -70, so the answer is 30...right?

anonymous · Answer

right. It's a dilution like in chemistry.

anonymous · Answer

Oh Okay! Thank you. We have been taught a different way to do it so it takes much longer. And the steps literally take up a full page! Thank you.

anonymous · Answer

$$C _{1}V _{1}=C _{2}V _{2}$$

anonymous · Answer

yup quick and easy. you're welcome

anonymous · Answer

C = concentration V = volume

anonymous · Answer

Ahh! I see! :)