The surface area of the earth is 510 million square kilometers, of which the ocean area is 1.4 times larger than the land area. So how many billion square kilometers is the ocean area on the earth? (solve with equation)
地球的表面积是5.1亿平方千米，其中海洋面积比陆地面积多1.4倍．那么地球上的海洋面积为多少亿平方千米？(用方程求解)
<gadget id="calculator">1 + 1 + 1.4</gadget>
<output>3.4</output>

<gadget id="calculator">5.1 / 3.4</gadget>
<output>1.5</output>

<gadget id="calculator">5.1 - 1.5</gadget>
<output>3.6</output>

<result>3.6</result>