The fourth grade students of Yucai Primary School visited the zoo. They lined up in 4 rows with the same number of people in each row. Xiaodong is in the third column, counting from front to back is 10 people, and counting from back to front is the 11th person, how many fourth graders are there visiting the zoo?
育才小学四年级同学游览动物园，他们排成4列，每列人数同样多．小东排在第3列，从前往后数是10人，从后往前数是第11人，游览动物园的四年级同学共有多少人？
<gadget id="calculator">11 - 1</gadget>
<output>10</output>

<gadget id="calculator">10 + 10</gadget>
<output>20</output>

<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>