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\begin{aligned} &\text{Oxidation:}\quad \ce{Cu}(s) \rightarrow \ce{Cu^2+}(aq) + 2\,e^- \\[0.75em] &\text{Reduction:}\quad \ce{MnO4-}(aq) + \ce{4H+}(aq) + 3\,e^- \rightarrow \ce{MnO2}(s) + \ce{2H2O}(l) \end{aligned}
When the half-reactions listed above are combined into a balanced chemical equation, the ratio of the coefficients $\ce{Cu}(s):\ce{MnO4-}(aq)$ is