Among the world's seven continents, Asia is the largest, accounting for about 3/10 of the total land area; followed by Africa, accounting for about 1/5 of the total land area, and the remaining five continents account for about 1/5 of the earth's land area. What fraction of the total area?
世界七大洲中面积最大的是亚洲，大约占陆地总面积的(3/10)；其次是非洲，大约占陆地总面积的(1/5)，其余五大洲的总面积约占地球陆地总面积的几分之几？
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(3/10) + (1/5)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>