The circumference of a circle is 100 cm. Two ants A and B start from the same place at the same time and crawl in the same direction. A’s speed is 3 cm per second. B crawls 20 cm and then turns around and crawls back. As a result, B crawls 40 cm past the starting point and meets A The second encounter. What is B's speed?
一个圆周长100厘米，甲、乙两只蚂蚁从同一地点同时出发同方向爬行，甲的速度是每秒3厘米，乙爬行20厘米后掉头往回爬，结果乙爬过出发点40厘米后与甲第二次相遇．乙的速度是多少？
<gadget id="calculator">100 - 40</gadget>
<output>60</output>

<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<gadget id="calculator">40 + 40</gadget>
<output>80</output>

<gadget id="calculator">80 / 20</gadget>
<output>4</output>

<result>4</result>