A certain book is 6 yuan each, buy 5 books and get 1 free, buy 5 books at a time, how much is each book cheaper?
某种书每本6元，买5本送1本，一次买5本，每本便宜多少元钱？
<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<gadget id="calculator">6 / 6</gadget>
<output>1</output>

<gadget id="calculator">5 * 1</gadget>
<output>5</output>

<gadget id="calculator">6 - 5</gadget>
<output>1</output>

<result>1</result>