Dongdong, Jingjing, and Honghong are going to measure their height and have their eyesight checked. Each check takes 3 minutes. How long will it take them at least to complete these checks?
东东、晶晶、红红三位同学要去量身高、验视力，每项检查都要3分钟，他们至少要用长时间能做完这些检查？
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<result>9</result>