Two athletes, Xiao Zhang and Xiao Wang, conduct race walking training. Xiao Zhang starts from A and Xiao Wang starts from B at the same time, and walks back and forth between the two places (they return immediately after arriving at another place). At a distance of 3.5 kilometers from A, their first They met once, and then met for the second time when Xiao Zhang left place B and was 3 kilometers away from place B. If they continue to walk like this, when they meet for the fourth time, how many kilometers away from place A will they be?
小张、小王两位运动员进行竞走训练，小张从甲地、小王从乙地同时出发，在两地之间往返行走(到达另一地后就马上返回)，在离甲地3.5千米处他们第一次相遇，又在小张离开乙地且距乙地3千米处第二次相遇，这样继续走下去，当他们第四次相遇时，距甲地多少千米．
<gadget id="calculator">3.5 * 3</gadget>
<output>10.5</output>

<gadget id="calculator">10.5 - 3</gadget>
<output>7.5</output>

<gadget id="calculator">7.5 * 4</gadget>
<output>30</output>

<gadget id="calculator">3 + 2 + 2</gadget>
<output>7</output>

<gadget id="calculator">3.5 * 7</gadget>
<output>24.5</output>

<gadget id="calculator">30 - 24.5</gadget>
<output>5.5</output>

<result>5.5</result>