JEE Main 2014 · 19 Apr · Shift 1, Chemistry question 44

Each $\ce{Cr2O7^2-}$ gains 6 electrons ($2\ce{Cr}$: +6 → +3). In the balanced reaction those 6 electrons come from $\ce{Fe^2+}$ (1 each) and $\ce{C2O4^2-}$ (2 each), e.g. with 2 $\ce{Fe^2+}$ and 2 $\ce{C2O4^2-}$. So 6 electrons are transferred, as keyed.