20 tons of yellow sand needs to be transported on the construction site: First, a truck with a load of 4 tons is used for three times, and the rest is transported with a cart with a load of 0.5 tons. How many times does the cart need to be transported?
工地上要运送20吨黄沙：先用一辆载重4吨的汽车运3次，剩下的用一辆载重为0.5吨的板车运，板车还需运几次？
<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">20 - 12</gadget>
<output>8</output>

<gadget id="calculator">8 / 0.5</gadget>
<output>16</output>

<result>16</result>