Mingming read "Fairy Tales", 19 pages on the first day, 21 pages on the second day, and 20 pages on the third day. How many pages does he read per day on average?
明明读《童话故事》，第一天读了19页，第二天读了21页，第三天读了20页．他平均每天读多少页．
<gadget id="calculator">19 + 21 + 20</gadget>
<output>60</output>

<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<result>20</result>