There are 500 trees in a batch, and the ratio of surviving trees to dead trees is 4:1. What is the survival rate?
一批树有500棵，成活棵树与死去棵树的比是4：1，成活率为多少．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

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

<gadget id="calculator">500 * (4/5)</gadget>
<output>400</output>

<gadget id="calculator">400 / 500</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>