If a rectangle with a length of 5 decimeters and a width of 4 decimeters is reduced by a ratio of 1:2, what is the area of the reduced rectangle?
把长5分米，宽4分米的长方形按1：2的比缩小，缩小后的长方形的面积是多少．
<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">(5/2) * 2</gadget>
<output>5</output>

<result>5</result>