The number A is the reciprocal of the number B. After the number B is enlarged by 10 times, it is 5. What is the number A?
甲数是乙数的倒数，乙数扩大10倍后是5，甲数是多少．
<gadget id="calculator">2 / 1</gadget>
<output>2</output>

<result>2</result>