A and B race around the circular runway. They walk from point A in the same direction at the same time. When A walks (1/5) of the distance, B walks 64 meters. When A returns to the starting point A , the ratio of the distance traveled by B to the whole journey is 4:5, find the total length of the circular runway.
甲、乙两人绕环形跑道竞走一圈，他俩同时从A点同向行走，在甲走完全程的(1/5)时，乙行了64米，当甲回到出发地A点时，乙行完的路程与全程的比为4：5，求这个环形跑道的全长．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(4/5) * (1/5)</gadget>
<output>4/25 = around 0.16</output>

<gadget id="calculator">64 / (4/25)</gadget>
<output>400</output>

<result>400</result>