It costs Xiao Ming 90 yuan to buy a set of clothes. The price ratio of jackets and trousers is 5:4, so it costs as much as a pair of trousers.
小明买一套服装要90元，上衣与裤子的价钱比是5：4，买一条裤子就花多少元．
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">90 * (4/9)</gadget>
<output>40</output>

<result>40</result>