A number of books are distributed to groups A and B, and each person can get 4 books; if only group A is distributed, each person can get 5 books. So, if it is only distributed to group B, how many copies can each person get?
有若干本书分给甲、乙两组，每人可分得4本；若果只分给甲组，每人可分得5本．那么，如果只分给乙组，每人可分得几本？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / (1/20)</gadget>
<output>20</output>

<result>20</result>