Answer
The decrease in launch speed when changing the angle from $30.00^{\circ}$ to $42.00^{\circ}$ is
$$\frac{12.76 \mathrm{\ m} / \mathrm{s}-12.54 \mathrm{\ m} / \mathrm{s}}{12.76 \mathrm{\ m} / \mathrm{s}}=0.0169=1.69\ \%$$
Work Step by Step
The decrease in launch speed when changing the angle from $30.00^{\circ}$ to $42.00^{\circ}$ is
$$\frac{12.76 \mathrm{\ m} / \mathrm{s}-12.54 \mathrm{\ m} / \mathrm{s}}{12.76 \mathrm{\ m} / \mathrm{s}}=0.0169=1.69\ \%$$
