The school planted a batch of trees. The ratio of the number of unsurviving trees to the number of surviving trees is 1:4. What is the survival rate of this batch of trees?
学校种一批树，未成活的棵数与成活的棵数的比是1：4，这批树的成活率是多少．
<gadget id="calculator">1 + 4</gadget>
<output>5</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(4/5) * 1</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>