The construction site needs to transport 122 tons of cement. After transporting 18 times with a truck with a load of 4 tons, how many times should the rest be transported with a truck with a load of 2.5 tons?
建筑工地要运122吨水泥，用一辆载重4吨的汽车运了18次后，余下的用一辆载重2.5吨的汽车运，还要运多少次？
<gadget id="calculator">4 * 18</gadget>
<output>72</output>

<gadget id="calculator">122 - 72</gadget>
<output>50</output>

<gadget id="calculator">50 / 2.5</gadget>
<output>20</output>

<result>20</result>