On June 1st, children's books in bookstores are sold at a 10% discount. The current price of a set of children's books is 360 yuan, so how much cheaper is it.
"六一"节，书店的儿童读物打九折出售，一套儿童读物的现价360元，那么便宜了多少元．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">360 / (9/10)</gadget>
<output>400</output>

<gadget id="calculator">400 - 360</gadget>
<output>40</output>

<result>40</result>