Chemistry redox titration question?

I don't have the time to give a full answer, but while you wait for someone to give you the answer, what you'll want to do is to find the chemical equation that was used in the reaction. From that you have a ratio of the number of moles of dichromate solution to iron moles. Convert the m of dichromate into moles, then change that to moles of iron, then convert to grams of iron, then find what the percentage of that is compared to the total m given.