A book has 21 pages. How much do you read 3 pages of this book every day on average?
一本书有21页，平均每天看这本书的3页，占全书的多少．
<gadget id="calculator">3 / 21</gadget>
<output>1/7 = around 0.142857</output>

<result>1/7 = around 0.142857</result>