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Eq. \ref{eq:3843961} is an initial equation. \begin{equation} V = I R \label{eq:3843961} \end{equation} Change variable \(V\) to \(V_1\) and \(R\) to \(R_1\) in Eq. \ref{eq:3843961}; yields Eq. \ref{eq:8012785}. I is the same across both resistors \begin{equation} V_1 = I R_1 \label{eq:8012785} \end{equation} Change variable \(V\) to \(V_2\) and \(R\) to \(R_2\) in Eq. \ref{eq:3843961}; yields Eq. \ref{eq:6379878}. \begin{equation} V_2 = I R_2 \label{eq:6379878} \end{equation}}})
Eq. \ref{eq:1124189} is an initial equation.
voltage is measured across both resistors
\begin{equation}
V_{\rm total} = V_1 + V_2
\label{eq:1124189}
\end{equation}
Eq. \ref{eq:4107950} is an initial equation.
\begin{equation}
V_{\rm total} = I R_{\rm total}
\label{eq:4107950}
\end{equation}
Substitute LHS of Eq. \ref{eq:4107950} and LHS of Eq. \ref{eq:8012785} and LHS of Eq. \ref{eq:6379878} into Eq. \ref{eq:1124189}; yields Eq. \ref{eq:4870091}.
\begin{equation}
I R_{\rm total} = I R_1 + I R_2
\label{eq:4870091}
\end{equation}
Divide both sides of Eq. \ref{eq:4870091} by \(I\); yields Eq. \ref{eq:5454988}.
\begin{equation}
R_{\rm total} = R_1 + R_2
\label{eq:5454988}
\end{equation}
Eq. \ref{eq:5454988} is one of the final equations.