A student used a calculator to calculate a problem. In the last step, he divided 10 and multiplied by 10 by mistake. Therefore, the wrong answer was 400. What should be the correct answer?
一个学生用计算器算题，在最后一步除似10，错误地乘10了，因此得出错误答案是400，正确答案应该是多少．
<gadget id="calculator">400 / 10</gadget>
<output>40</output>

<gadget id="calculator">40 / 10</gadget>
<output>4</output>

<result>4</result>