The land area on the earth is 150 million square kilometers, and the ocean area is about 2.4 times the land area. What is the surface area of the earth in billions of square kilometers?
地球上的陆地面积为1.5亿平方千米，海洋面积约为陆地面积的2.4倍．地球表面积是多少亿平方千米？
<gadget id="calculator">1.5 * 2.4</gadget>
<output>3.6</output>

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

<result>5.1</result>