There are 10 students in the first team of Class 1, Class 6. Whenever the holidays come, every two people talk on the phone once. I wish each other a happy holiday. During the National Day, they talked on the phone as agreed. How many times did they call in total? How many
六1班第一小队有10个同学．它们月的每当节日来临，每两人通电话一次．互祝节日快乐，国庆节期间，他们按照约定通电话，一共通了多少次电话？多少
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">9 * 5</gadget>
<output>45</output>

<result>45</result>