There is a barrel of gasoline, which was planned to last for 20 days, but actually used 3 kilograms of gasoline per day, and the result was 10 days more than planned. How many kilograms of gasoline was originally planned to be used per day?
有一桶汽油，计划可以用20天，实际每天用汽油3千克，结果比计划多用了10天，原计划每天用汽油多少千克？
<gadget id="calculator">3 * 20</gadget>
<output>60</output>

<gadget id="calculator">3 * 10</gadget>
<output>30</output>

<gadget id="calculator">60 + 30</gadget>
<output>90</output>

<gadget id="calculator">90 / 20</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>