Two people, A and B, are running a 100-meter race. When A reaches the finish line, B has run 80 meters. If the speed of the two remains the same, in order for them to reach the finish line at the same time, how many meters should A's starting line be moved back from the original starting line?
甲、乙两人进行百米赛跑，当甲到达终点时，乙跑了80米，如果两人的速度不变，要使两人同时到达终点，甲的起跑线应比原起跑线后移多少米？
<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">100 * (5/4)</gadget>
<output>125</output>

<gadget id="calculator">125 - 100</gadget>
<output>25</output>

<result>25</result>