Algebra
# Exponential Functions

$pH$ measures the concentration of hydrogen ions $H^+$ in a solution. Let $pH=m$ if the number of gram ions of $H^+$ in a $1$-liter solution is $10^{-m}$.

Then the ratio of the number of gram ions of $H^+$ for $pH=6.5$ and the number of gram ions of $H^+$ for $pH=7.9$ can be expressed as $10^a.$ What is the value of $100a?$