Outline a plan of an experiment to determine the percentage of iron present as iron(III) in a solution containing $\ce{Fe^3+(aq)}$ and $\ce{Fe^2+(aq)}$ ions. You are provided with zinc, a standard solution of potassium dichromate(VI) and dilute sulfuric acid. How you would use the zinc and how you would calculate the final answer.
So I know that the following equations will be involved
$\ce{2Fe^3+ + Zn -> 2Fe^2+ + Zn^2+}$
$\ce{6 Fe^2+ + Cr2O7^2- + 14 H+ → 6 Fe^3+ + 2 Cr^3+ + 7 H2O}$
I am very unsure on the method to use, I know that I can titrate a sample of the solution against $\ce{K2Cr2O7}$ to eliminate $\ce{Fe2+}$ ions, but I am clueless on how to proceed after.