40 students were divided into one group of composition books on average, and then 10 more students came, and everyone redistributed, and each person got 3 fewer composition books than before. How many copies are there in total?
40个同学平均分一批作文本，后来又来了10人，大家重新分配，每人分得的作文本比原来少了3本．这批作文本共有多少本？
<gadget id="calculator">3 * 40</gadget>
<output>120</output>

<gadget id="calculator">3 * 10</gadget>
<output>30</output>

<gadget id="calculator">120 + 30</gadget>
<output>150</output>

<gadget id="calculator">1 / 40</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">(1/40) * 40</gadget>
<output>1</output>

<gadget id="calculator">(1/40) * 10</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/4) - 1</gadget>
<output>-3/4 = around -0.75</output>

<gadget id="calculator">1 + (-3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">150 / (1/4)</gadget>
<output>600</output>

<result>600</result>