<p>HI
Can you help me solve this one:</p>
<p>THe circle pictured has a center O and diameter AB, the two semi circles have diameters OA and OB</p>
<p>If the circumference of the circle is 36pi what is the length of the curved path from A to B through O.</p>
<p>Possible answers:</p>
<p>6pi
9pi
18pi
24pi
36pi</p>
<p>circumference = diameter * pi</p>
<p>So you know the diameter of the big circle is 36. You also know that the diameter of each little semi-circle is 18 since each diameter of the semi-circles is the length of the radius of the big circle. </p>
<p>So the circumference of the little circles (if you drew in the other half to complete the semi-circle) would be 18pi. But these are semi-circles so you have to dived 18pi by 2. But since there are two semi-circles you multiply it by 2 to get 18pi as the final answer. (you can cancel out the last two steps)</p>