Xiao Ming buys a book at the original price of 2.85 yuan, and the bookstore sells it to Xiao Ming at a discount of 20% of the original price. How much does Xiao Ming pay?
小明买一本书原价2.85元，书店按原价八折卖给小明，小明付了多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">2.85 * (4/5)</gadget>
<output>2.28</output>

<result>2.28</result>