The circumference of a circle is 70 cm. Two reptiles A and B start from the same point at the same time and crawl in the same direction. A crawls continuously at a speed of 4 cm/s. After B crawls 15 cm, he immediately crawls in the opposite direction, and the speed increases by 1 times, meet A at a distance of 30 cm from the starting point, and ask reptile B's original speed in cm/s.
一个圆周长70厘米，甲、乙两只爬虫从同一点同时出发，同向爬行，甲以4厘米/秒的速度不停地爬行，乙爬行15厘米后，立即反向爬行，并且速度增加1倍，在离出发点30厘米处与甲相遇，问爬虫乙原来的速度是多少厘米/秒．
<gadget id="calculator">30 + 45</gadget>
<output>75</output>

<gadget id="calculator">70 - 30</gadget>
<output>40</output>

<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">75 / 20</gadget>
<output>15/4 = around 3.75</output>

<result>15/4 = around 3.75</result>