The ratio of the length of a canal that has been built to the length that has not been built is 4:1, how much has this canal been built
一条水渠已修的和未修的长度的比是4：1，这条水渠已修了多少
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

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

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