5 children in the third grade, during the summer vacation, every 2 people make a phone call, how many times will they have to make a phone call in total?
三年级的5位小朋友，暑假期间每2人通一次电话，一共要通多少次电话．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">4 * (5/2)</gadget>
<output>10</output>

<result>10</result>