There are 45 classes in Xinguang Primary School this year, which is 10% less than last year. How many classes were there last year?
新光小学今年有45个班，比去年的班数减少10%，去年有多少个班？
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">45 / (9/10)</gadget>
<output>50</output>

<result>50</result>