When the New Year is here, 40 students in Class 1 of Class 6 give each other New Year's cards, so how many New Year's cards did the class buy in total?
新年到了，六1班40名同学互赠贺年卡，则该班共购买了多少张贺年卡．
<gadget id="calculator">40 - 1</gadget>
<output>39</output>

<gadget id="calculator">40 * 39</gadget>
<output>1_560</output>

<result>1_560</result>