Answer :
You are right.
Here's an easier way to do it :
We have an initial solution of concentration [tex]C[/tex].
We want to turn it into a [tex]V[/tex] mL solution of concentration [tex]C_1[/tex], and we want to know which volume [tex]V_1[/tex] of solution to take from the original to do that.
We know that [tex]C_1=C\frac{V_1}V[/tex] hence [tex]V_1=\frac{C_1}CV=\frac{0.5}4250=\frac{250}8=31.25 mL[/tex]
Here's an easier way to do it :
We have an initial solution of concentration [tex]C[/tex].
We want to turn it into a [tex]V[/tex] mL solution of concentration [tex]C_1[/tex], and we want to know which volume [tex]V_1[/tex] of solution to take from the original to do that.
We know that [tex]C_1=C\frac{V_1}V[/tex] hence [tex]V_1=\frac{C_1}CV=\frac{0.5}4250=\frac{250}8=31.25 mL[/tex]