## Thinking Mathematically (6th Edition)

$2.1 \times 10^3$
Write each number in scientific notation to obtain: $=\dfrac{8.4 \times 10^6}{4 \times 10^{3}}$ Divide 8.4 and 4 together and the powers of 10 together to obtain: $=\dfrac{8.4}{4} \times \dfrac{10^6}{10^3} \\=2.1 \times 10^{6-3} \\=2.1 \times 10^3$