One car can transport 18 tons of coal three times. According to this calculation, how many cars are needed to transport a pile of 90 tons of coal at one time?
一辆汽车3次可运煤18吨，照这样计算，一堆煤90吨，需要多少辆汽车一次运完？
<gadget id="calculator">18 / 3</gadget>
<output>6</output>

<gadget id="calculator">90 / 6</gadget>
<output>15</output>

<result>15</result>