Xiaohong wants to buy a book with an original price of 15 yuan at the bookstore, and it is now on sale at a 40% discount. How much is it cheaper for Xiaohong to buy this book?
小红在书店想买一本原价15元的书，现在打六折出售．小红买这本书便宜了百分之几？
<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>