A truck transports cement. On the first day, it transports a total of 42 tons of cement in 5 times, and in the second day, it transports 5.4 tons of cement in 7 times each time. How many tons of cement does this truck transport on average per day?
一辆卡车运水泥，第一天5次共运水泥42吨，第二天7次每次运水泥5.4吨，这辆卡车平均每天运水泥多少吨？
<gadget id="calculator">7 * 5.4</gadget>
<output>37.8</output>

<gadget id="calculator">42 + 37.8</gadget>
<output>79.8</output>

<gadget id="calculator">79.8 / 2</gadget>
<output>39.9</output>

<result>39.9</result>