Explanation:
what is the problem ?
your teacher even wrote the formula into the question.
so, now we only need to do the multiplications of the formula to get the result.
you have no calculator ?
the area is pi×r²
r = 10 in
and we are told to approximate pi as being 3.14.
so, the area is
3.14 × 10² = 3.14 × 100 = 314 in²