A parachute falls from a height of 18,000 meters at a speed of 10 meters per second. At the same time, a hot air balloon rises from the ground. After 20 minutes, the umbrella balls meet in the air. How many meters per second does the hot air balloon rise?
降落伞以每秒10米的速度从18000米高空下落，与此同时有一热气球从地面升起，20分钟后伞球在空中相遇，热汽球每秒上升多少米？
<gadget id="calculator">1_200 * 10</gadget>
<output>12_000</output>

<gadget id="calculator">18_000 - 12_000</gadget>
<output>6_000</output>

<gadget id="calculator">6_000 / 1_200</gadget>
<output>5</output>

<result>5</result>