Draw 10 rays from a point, how many angles less than 180° can be counted.
从一点引出10条射线，可以数出多少个小于180°的角．
<gadget id="calculator">1 + 9</gadget>
<output>10</output>

<gadget id="calculator">9 / 2</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">10 * (9/2)</gadget>
<output>45</output>

<result>45</result>