My mother bought a barrel of 4L oil, and 200ml is used for cooking every day. How many days can this barrel of oil last?
妈妈买了一桶油共4L，每天炒菜用去200ml，这桶油能用多少天．
<gadget id="calculator">4 * 1_000</gadget>
<output>4_000</output>

<gadget id="calculator">4_000 / 200</gadget>
<output>20</output>

<result>20</result>