The tortoise and the hare run a race of 2000 meters, the tortoise climbs 20 meters per minute, and the rabbit runs 200 meters per minute. The rabbit thought it was running fast, so it fell asleep on the way, but when the tortoise reached the finish line, the rabbit was still 20 meters away from the finish line. How many minutes did the rabbit sleep for?
龟兔赛跑，全程2000米，乌龟每分钟爬20米，兔子每分钟跑200米．兔子自以为跑得快，在途中睡了一觉，结果乌龟到终点时，兔子离终点还有20米．兔子睡了多少分钟？
<gadget id="calculator">2_000 / 20</gadget>
<output>100</output>

<gadget id="calculator">2_000 - 20</gadget>
<output>1_980</output>

<gadget id="calculator">1_980 / 200</gadget>
<output>99/10 = around 9.9</output>

<gadget id="calculator">100 - (99/10)</gadget>
<output>901/10 = around 90.1</output>

<result>901/10 = around 90.1</result>