This year's "3•12" Arbor Day, Class 1 of June participated in the tree planting activity, but 4 trees failed to survive. It is known that the survival rate of these trees is 95%. How many trees were planted in Class 1?
今年"3•12"植树节，六1班参加了植树活动，后来有4棵没成活．已知这些树的成活率是95%，六1班一共栽了多少棵树．
<gadget id="calculator">95 / 100</gadget>
<output>19/20 = around 0.95</output>

<gadget id="calculator">1 - (19/20)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">4 / (1/20)</gadget>
<output>80</output>

<result>80</result>