When Xiaohong is running, first increase the speed (1/10) and then decrease the speed (1/10). At this time, the speed is 247.5 m/min. What is the original speed in m/min?
小红跑步，先提速(1/10)，后降速(1/10)，这时速度为247.5米/分，则原速是多少米/分．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 + (1/10)</gadget>
<output>11/10 = around 1.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(11/10) * (9/10)</gadget>
<output>99/100 = around 0.99</output>

<gadget id="calculator">247.5 / (99/100)</gadget>
<output>250</output>

<result>250</result>