Answer
$$A = 3,001,500\ mi^2$$
Work Step by Step
We first find the area of each hurricane. Assuming them to be approximately circular, we find:
Sandy: $A= \pi(1000 \ mi )^2 \\ A = 3,140,000 \ mi^2$
Katrina: $A= \pi (210\ mi)^2 \\ A = 138,500 \ mi^2$
Thus, the difference to the nearest 100 square miles is:
$$ A= 3,140,000 - 138,500 \\ A = 3,001,500\ mi^2$$
