divide and write the result using scientific notation (4.0 x 10^7) / (5.0 x 10^9)

divide and write the result using scientific notation (4.0 x 10^7) / (5.0 x 10^9)

$$\small{\text{ $ \begin{array}{rcl} \dfrac{4.0 \cdot 10^7} {5.0 \cdot 10^9} & \\ &=& \dfrac{4.0}{5.0} \cdot 10^7\cdot 10^{-9} \\ &=& 0.8 \cdot 10^{7-9} \\ &=& 0.8 \cdot 10^{-2} \\ &=& \dfrac{8}{10} \cdot 10^{-2} \\ &=& 8 \cdot \dfrac{ 10^{-2}}{10} \\ &=& 8 \cdot 10^{-2}\cdot 10^{-1} \\ &=& 8 \cdot 10^{-2-1} \\ &=& 8 \cdot 10^{-3 } \end{array} $}}$$

40000000/5000000000=0.08

4/5= 0.8

7-9=-2

0.8*(10^-2)=8*(10^-3)=0.08.