and B are traveling opposite each other from A and B respectively. The speed of A is 60 km/h, and the speed of B is 40 km/h. They set off for 4 hours. When they meet, A exceeds the midpoint by 180 km. Find the distance between A and B.
甲、乙分别从A、B对行，甲速60千米/时，乙速40千米/时，出发4小时，相遇时甲超过中点180千米，求AB之间的距离．
<gadget id="calculator">60 - 40</gadget>
<output>20</output>

<gadget id="calculator">2 / 20</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">60 + 40</gadget>
<output>100</output>

<gadget id="calculator">180 * (1/10) * 100</gadget>
<output>1_800</output>

<result>1_800</result>