#### Answer

The percent increase is 25%.

#### Work Step by Step

To find the percent change, we use the following formula:
Percent of change = $\frac{New\ amount\ -\ Original\ amount}{Original\ amount}$ $\times$ 100%
The original length was 8 centimeters, and the new length is 10 centimeters.
Substituting these values into the formula yields:
Percent change = $\frac{10-8}{8}$ $\times$ 100%
Percent change = $\frac{2}{8}$ $\times$ 100%
Percent change = 0.25 $\times$ 100%
Percent change = 25%