Divide 153 by 13 which is 51.
There is no need to round to the nearest tenths
Answer:

Step-by-step explanation:
The square is in the circle, so the diameter is the diagonal line of the square. This divides the square into two right triangles.
Two sides of the right triangle equal 8. This qualifies it as a special right triangle. This triangle has two sides that = x (in this case 8) and the hypotenuse is
.
Substitute 8 in for x.
is the diameter, so we divide in half to get the radius = 
Answer:
C
Step-by-step explanation:
The distance around the circle is asking for the circumference of the circle.
Since we know that the diameter is 21 and the equation for the circumference of a circle is 2*pi*r and since 2*r is just the diameter, we can say that the circumference is 21*pi, which would be C.
Can us show us the problems.