Four classes of the third grade participated in the activity of welcoming the aerospace heroes report group. Each class selected 15 people, and each person needed 2 balloons. How many balloons are needed in total?
三年级4个班参加欢迎航天英雄报告团活动，每个班选15人，每人需要2个气球，一共需要多少个气球？
<gadget id="calculator">15 * 4 * 2</gadget>
<output>120</output>

<result>120</result>