Each oil barrel can hold up to 3.5 kilograms of oil, and 20 kilograms of oil. How many such oil barrels are needed at least?
每个油桶最多可以装3.5千克油，装20千克油，至少需要多少个这样的油桶？
<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<result>6</result>