The school plans to use 400 yuan to make screen windows for 21 classrooms. If each classroom needs 25 yuan, how much is the difference?
学校准备用400元给21个教室做纱窗，如果每间教室需要25元，还差多少元．
<gadget id="calculator">25 * 21</gadget>
<output>525</output>

<gadget id="calculator">525 - 400</gadget>
<output>125</output>

<result>125</result>