$\text{100 kWh}=$_________ erg     

$\text{100 kwh}\to \text{erg}$

$\text{1kwh}=3.6\times {10}^6\text{J}$                 $(\therefore 1\text{\hspace{0.17em}J}={10}^7\text{erg})$

$=\text{3.6}\times {\text{10}}^6\times {10}^7\text{erg}$

$\text{1Kwh}=3.6\times {10}^{13}\text{erg}$

$\text{100kwh}=\text{100}\times \text{3.6}\times {\text{10}}^{\text{13}}\text{erg}\Rightarrow {\text{3.6×10}}^{15}\text{erg}$