Final answer:
The percentage of the total population of the US that was foreign born in 2010 was 13.0%.
Step-by-step explanation:
To find the percentage of the total population of the US that was foreign-born in 2010, you need to divide the number of foreign-born people (40 million) by the total population of the US (269.4 million + 40 million) and then multiply by 100 to convert it to a percentage.
The total population of the US in 2010 was 269.4 million + 40 million = 309.4 million. So, the percentage of the total population that was foreign-born is (40 million / 309.4 million) * 100 = 12.9%, which rounds to the nearest tenth of a percent as 13.0%.