The construction of a building in Chengxi Primary School is planned to cost 4 million yuan, but the actual saving is 10% compared with the original plan. How much is the savings?
城西小学建一幢大楼，计划用去400万元，实际比原计划节约10%，节约多少万元？
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">400 * (1/10)</gadget>
<output>40</output>

<result>40</result>