Susan is creating a solution. A formula for the solution calls for 7/10 mL of water. Susan wants to make 2/7 less of the solution than the formula creates.

How much water should Susan use?

Express your answer as a fraction in simplest form.

Question

Susan is creating a solution. A formula for the solution calls for 7/10 mL of water. Susan wants to make 2/7 less of the solution than the formula creates.
 
How much water should Susan use?
 
Express your answer as a fraction in simplest form.

faiqraees · Answer

So susan wants to make 5/7 of the solution of the formula right?

twistrose · Answer

yeah

calculusxy · Answer

I think that we can make a proportion in here. 
$$\large \frac{ 1 }{ \frac{7}{10} } = \frac{ 1 - \frac{2}{7} }{ x }$$

1 represents the total solution 
7/10 is the amount of water required for that total solution 

1 - 2/7 shows that she wants to make 2/7 less than the total solution
x  is the amount of water that you are looking for for the 1- 2/7 mL of solution

faiqraees · Answer

Okay so the solution of the formula create 7/10ml
SO  5/7 of the solution of the formula = 5/7 x 7/10

calculusxy · Answer

@Twistrose do you understand the proportion that I made?

twistrose · Answer

no i dont understand that

faiqraees · Answer

Do you understand my method?

twistrose · Answer

yeah i understand that better

faiqraees · Answer

Good @calculusxy method is just a complicated version of my method.

twistrose · Answer

oh ok

faiqraees · Answer

Okay so multiply 5/7 by 7/10 what do you get?

twistrose · Answer

35/70

faiqraees · Answer

Now simplify it

calculusxy · Answer

Yes in a way it is:
|dw:1459012751178:dw|

which is the same thing as 
$\large \frac{7}{10} \times \frac{5}{7}$