A, B, and C are running a three-person race. A and B race for 100 meters. When A reaches the finish line, B only runs 90 meters. B and C race for 100 meters. When B reaches the finish line, C also only runs 90 meters. A and C run 100 meters. When A reaches the finish line, how many meters does C run?
甲乙丙三人赛跑，甲和乙比赛跑100米，甲到终点时，乙只跑了90米，乙和丙比赛跑100米，乙到终点时，丙也只跑了90米，那么假如甲和丙跑100米，甲到终点时，丙跑了多少米？
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">100 * (9/10) * (9/10)</gadget>
<output>81</output>

<result>81</result>