Cars A and B start from A and B respectively, and travel between A and B continuously. It is known that the speed of car A is 15 km/h, and the speed of car B is 35 km/h. The difference between the third meeting point and the fourth meeting point of the two cars is 100 km. Find the distance between A and B.
甲、乙两车分别从A、B两地出发，并在A，B两地间不断往返行驶．已知甲车的速度是15千米/小时，乙车的速度是35千米/小时，甲、乙两车第三次相遇地点与第四次相遇地点相差100千米．求A、B两地的距离．
<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<gadget id="calculator">9 - 5</gadget>
<output>4</output>

<gadget id="calculator">100 / 4</gadget>
<output>25</output>

<gadget id="calculator">25 * 10</gadget>
<output>250</output>

<result>250</result>