The surface area of the earth is approximately equal to 510 million square kilometers, of which 71% is water and 29% is land. How many million square kilometers is the land area less than the water surface area?
地球的表面积约等于5.1亿平方千米，其中71%为水面，29%为陆地．陆地面积比水面面积少多少亿平方千米？
<gadget id="calculator">71 / 100</gadget>
<output>71/100 = around 0.71</output>

<gadget id="calculator">29 / 100</gadget>
<output>29/100 = around 0.29</output>

<gadget id="calculator">(71/100) - (29/100)</gadget>
<output>21/50 = around 0.42</output>

<gadget id="calculator">5.1 * (21/50)</gadget>
<output>2.142</output>

<result>2.142</result>