What Are Logarithmic Scales?

The apparent brightness of stars is measured on a logarithmic scale called magnitude, in which lower numbers mean brighter stars. The relationship between the ratio of apparent brightness of two objects and the difference in their magnitudes is given by the formula $m_2-m_1=-2.5\log\frac{b_2}{b_1}$, where $m$ is the magnitude and $b$ is the apparent brightness. How many times brighter is a magnitude $1.0$ star than a magnitude $2.5$ star?