Answer
2 $\times$ $10^{-3}$
Work Step by Step
You have the expression $\frac{4.2 * 10^8}{2.1 * 10^1{^1}}$.simplify the expression:
$\frac{4.2 * 10^8}{2.1 * 10^1{^1}}$=2$\times$$10^{8-11}$ -subtract the exponents and divide powers with the same base-
=2 $\times$ $10^{-3}$
