Question

Can someone please explain this for me, thank you.

Answer 1

just divide Atlantic/Mississippi

$\frac{3.1 \times {10}^{17} }{6.3 \times {10}^{11} } = \frac{3.1}{6.3} \times \frac{ {10}^{17} }{ {10}^{11} } \\ = 0.492 \times {10}^{17 - 11} \\ = 0.492 \times {10}^{6} \\ = 4.92 \times {10}^{5}$