A rectangular piece of land is 80 meters long and 40 meters wide. If the width is increased by 5 meters, how many meters should the length be reduced to keep the area constant?
一块长方形地，长是80米，宽是40米．如果把宽增加5米，要使面积不变，长应该减少多少米．
<gadget id="calculator">40 + 5</gadget>
<output>45</output>

<gadget id="calculator">40 / 45</gadget>
<output>8/9 = around 0.888889</output>

<gadget id="calculator">80 * (8/9)</gadget>
<output>640/9 = around 71.111111</output>

<gadget id="calculator">80 - (640/9)</gadget>
<output>80/9 = around 8.888889</output>

<result>80/9 = around 8.888889</result>