The blackboard in the classroom is 3 meters long and 1 meter wide. How many meters of wooden strips are needed to put wooden strips around the blackboard?
教室里的黑板长是3米，宽是1米．要在黑板的四周围上木条，需要木条多少米？
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<result>8</result>