The original price of "Mathematics Fun" is 16 yuan, but now it only costs 10% off, which is much cheaper than the original price.
一本《数学趣味》原价16元，现在只花了九折的钱，比原价便宜了多少元．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">16 * (1/10)</gadget>
<output>8/5 = around 1.6</output>

<result>8/5 = around 1.6</result>