A certain particle carries 2.5 x 10^-16 C of static electric charge. Calculate the number of electrons present in it.

$$\begin{gathered} \text{ Charge on one particle }=1.6022\times {10}^{-19}\mathrm{C} \\ \text{ Charge on }\mathrm{N}\text{ particles }=1.6022\times {10}^{-19}\times \mathrm{N}\text{ C } \\ \text{ Total charge }=2.5\times {10}^{-16}\mathrm{C} \\ \text{ Thus, }1.6022\times {10}^{-19}\mathrm{N}=2.5\times {10}^{-16} \end{gathered}$$
$\mathrm{N}=\frac{2.5\times {10}^{-16}}{1.6022\times {10}^{-19}}=1560$