Answer
$1.6\times10^{11}$
Work Step by Step
We start with the given expression: $(4\times10^5)^2$
To raise a product to a power, we raise each factor to the power and multiply: $4^2\times(10^5)^2$
To raise a power to a power, we multiply the exponents. $16\times10^{10}$
We write the expression in scientific notation: $1.6\times10^{11}$
