A total of 180 trees were planted in Jingyou Village this year, 20 of which did not survive, and another 20 were replanted immediately, and all of them survived. What is the survival rate of these trees?
径游村今年共植树180棵，有20棵没有成活，马上又补种了20棵，全部成活，求这批树的成活率是多少？
<gadget id="calculator">180 - 20</gadget>
<output>160</output>

<gadget id="calculator">160 + 20</gadget>
<output>180</output>

<gadget id="calculator">180 + 20</gadget>
<output>200</output>

<gadget id="calculator">180 / 200</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>