$\begin{array}{1 1}k[A]^3 [B]^3 \\ k[A][B]^3 \\ k[A]^3 [B] \\ k[A][B] \end{array}$

$\begin{array} {cccc}
\text{Experiment} & [A]\; \text{in M} & [B]\; \text{in M} & \text{Initial Rate in Ms}^{-1}\\
1 & 1 & 2 & 0.01\\
2 & 1 & 8 & 0.64\\
3 & 0.5 & 8 & 0.32\\
4 & 1 & 1 & 0.00125\\
\end{array}$

$\begin{array}{1 1}k[A]^3 [B]^3 \\ k[A][B]^3 \\ k[A]^3 [B] \\ k[A][B] \end{array}$

Answer: k[A][B]$^3$

Comparing experiments 2 and 3, with [B] constant, as [A] is halved, so does the initial rate. Hence rate is first order with respect to [A].

Comparing experiments 1 and 2, with [A] constant, as [B] increases 4 times, the initial rate increases 64 times (4$^3$), which means that the rate is third order with respect to [B].

Hence the Rate = k[A][B]$^3$

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