General formula for circles at the origin is x^2+y^2=R^2 where R is the radius.So R^2=4225. Solve for R.
The tenth place is the first number to the right of a decimal. To determine if you're rounding or not, check the hundred's place, 2 numbers to the right of a decimal, for 5 or higher. If it's .45, round to .5, if it's .44, round to .4
Your answer is 524.5, which is B.)
