Tickets for an amusement park used to be 45 yuan each, and there was a 10% discount during the "June 1st" period, so how much can you save by buying a ticket?
某游乐场的门票原来每张45元，"六一"期间九折优惠，则购买一张门票能省多少元．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">45 * (1/10)</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>