The bookstore has a sales promotion on "October", each science book is 30 yuan, buy 5 books and get 1 free; Uncle Zhang bought 6 books, how much is each book combined?
书店"十一"搞促销，每本科技书30元，买5本送1本；张叔叔买了6本书，每本合多少元？
<gadget id="calculator">5 + 1</gadget>
<output>6</output>

<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">30 * (5/6)</gadget>
<output>25</output>

<result>25</result>