Chapter 2 Atoms, Molecules, and Ions - Study Questions - Page 95: 9

$m_e/m_p=5.446\times10^{-4}$ $83.6\%$ above.

From table 2-1: $m_e=9.109383\times10^{-28}\ g$ $m_p=1.672622\times10^{-24}\ g$ their ratio is $m_e/m_p=5.446\times10^{-4}$ the percent error is: $\dfrac{0.001-5.446\times10^{-4}}{5.446\times10^{-4}}\times100\%=83.6\%$ The absolute error is quite small, but the relative error is substantial.