If it takes 7.8 minutes to roll a large snowball, how many minutes will it take to roll 4 identical large snowballs?
如果滚一个大雪球需要7.8分钟，滚了一模一样的大雪球4个，共需要几分钟呢？
<gadget id="calculator">7.8 * 4</gadget>
<output>31.2</output>

<result>31.2</result>