A squirrel can pick 24 pine cones per day on sunny days, but only 10 on rainy days. It has picked 280 pine cones for several consecutive days, with an average of 20 per day. How many of these days are rainy days?
一只松鼠采松果，晴天每天可采24个，雨天只能采10个，它一连多天采了280个松果，平均每天采20个，这些天中有多少天是雨天？
<gadget id="calculator">280 / 20</gadget>
<output>14</output>

<gadget id="calculator">24 * 14</gadget>
<output>336</output>

<gadget id="calculator">336 - 280</gadget>
<output>56</output>

<gadget id="calculator">24 - 10</gadget>
<output>14</output>

<gadget id="calculator">56 / 14</gadget>
<output>4</output>

<result>4</result>