If there are 20 points on a line segment, how many different line segments are there?
一条线段上有20个分点，共有多少条不同的线段．
<gadget id="calculator">20 + 2</gadget>
<output>22</output>

<gadget id="calculator">22 - 1</gadget>
<output>21</output>

<gadget id="calculator">21 / 2</gadget>
<output>21/2 = around 10.5</output>

<gadget id="calculator">22 * (21/2)</gadget>
<output>231</output>

<result>231</result>