## Elementary Technical Mathematics

$11.30\%$
First, find the increase in voltage by subtracting the voltage after the surge from the one before it: $=128 - 115 \\=13$ RECALL: $\text{percent increase}=\dfrac{\text{increase in value}}{\text{original value}}$ The given problem has: original value =$115$ volts increase in value = $13$ volts Sove for the percent increase using the formula above to obtain: percent increase $= \dfrac{13}{115} \\=0.1130434783 \\=0.1130434783 \times 100\% \\\approx 11.30\%$ Thus, there was an $11.30\%$ increase in voltage during the surge.