The object falls from the air, falls 4.9 meters in the first second, and then falls 9.8 meters more than the previous second every second, and reaches the ground after 10 seconds. How far is the object from the ground?
物体从空中落下，第一秒落下4.9米，以后每秒比前一秒多落下9.8米，经过10秒到地面．物体离地面多少米．
<gadget id="calculator">10 - 1</gadget>
<output>9</output>

<gadget id="calculator">9.8 * 9</gadget>
<output>88.2</output>

<gadget id="calculator">4.9 + 88.2</gadget>
<output>93.1</output>

<gadget id="calculator">93.1 + 4.9</gadget>
<output>98</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">98 * 5</gadget>
<output>490</output>

<result>490</result>