Assuming that the growth rate of the newly generated resources on the earth is constant, according to this calculation, the resources on the earth can support the life of 11 billion people for 90 years, or 210 years for 9 billion people. In order to enable human beings to continue to multiply, how many billions of people can the earth support at most?
假设地球上的新生成的资源的增长速度是一定的，照此测算，地球上资源可供110亿人生活90年，或可供90亿人生活210年．为使人类能够不断繁衍，那么地球最多能养活多少亿人．
<gadget id="calculator">90 * 210</gadget>
<output>18_900</output>

<gadget id="calculator">110 * 90</gadget>
<output>9_900</output>

<gadget id="calculator">18_900 - 9_900</gadget>
<output>9_000</output>

<gadget id="calculator">210 - 90</gadget>
<output>120</output>

<gadget id="calculator">9_000 / 120 / 1</gadget>
<output>75</output>

<result>75</result>