Black and white TV sets are (4/5) of color TV sets, and color TV sets are ((())/(())) of the total number of two types of TV sets.
黑白电视机是彩电的(4/5)，彩电是两种电视机总数的((())/(()))．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 + (4/5)</gadget>
<output>9/5 = around 1.8</output>

<gadget id="calculator">1 / (9/5)</gadget>
<output>5/9 = around 0.555556</output>

<result>5/9 = around 0.555556</result>