It took 6 minutes to weld 3 steel bars into a long steel bar. According to this calculation, how many minutes will it take to weld 4 steel bars into a long steel bar.
将3根钢筋焊接成一根长钢筋用了6分钟，照这样计算，将4根钢筋焊接成一根长钢筋需要多少分钟．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<result>9</result>