During the "June 1st" period, the park tickets are 20% off, and children's tickets are 4 yuan a piece, which is how much less than the original price.
"六一"期间，公园门票八折优惠，儿童票4元一张，比原来降价多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">5 - 4</gadget>
<output>1</output>

<result>1</result>