After a piece of firewood has been sawed 4 times, the average length of each section is 4 meters. What is the original total length of the firewood?
一根木柴被锯了4次后，平均每段长4米，这根木柴原来总长多少米．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<result>20</result>