A, B, and C each start from A to B at a certain speed at the same time. When A arrives at B, B has traveled the entire distance (9/10), and C is still (1/10) from B. 5), when B arrives at B, how much does C walk the whole way.
甲、乙、丙三人各自以一定的速度同时从A地出发走向B地，当甲到达B地时，乙走了全程的(9/10)，丙离B地还有全程的(1/5)，当乙到达B地时丙走了全程的多少．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(4/5) / (9/10)</gadget>
<output>8/9 = around 0.888889</output>

<result>8/9 = around 0.888889</result>