The measured value is $L = 2.5 \text{ m}$. The absolute error is $\Delta L = 0.05 \text{ m}$. Fractional error is given by $\frac{\Delta L}{L} = \frac{0.05}{2.5}$. $\frac{0.05}{2.5} = \frac{5}{250} = \frac{1}{50} = 0.02$. Percentage error is the fractional error multiplied by $100\%$: Percentage error $= 0.02 \times 100\% = 2.0\%$.