The proposition teacher is Classes 1-6 of the fifth grade, preparing Olympic mathematics test questions. Each class has 7 questions, and exactly 4 questions are different from any other class. Just ask, how many different test questions should be prepared at most?
命题老师为五年级1～6班，准备奥林匹克数学试题，每个班各7题，而且都恰有4题跟任何其它班不同．试问，最多要准备多少题不同的试题？
<gadget id="calculator">4 * 6</gadget>
<output>24</output>

<gadget id="calculator">3 * 6</gadget>
<output>18</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">24 + 9</gadget>
<output>33</output>

<result>33</result>