Complete Solution:

Based on the low estimate, the US population will not double by 2100.

Based on the middle and high estimates, it will more than double.

None of the estimates shows a 400% increase.

The estimated US population in 2000 was about 275 million people. Note that a 100% increase is the same as doubling which gives 550 million people. An increase of 400% would mean the 2000 population plus 4 times the population.

275,000,000 + (4 × 275,000,000) or
5 × 275,000,000,
which is 1,375,000,000 people.

Comparing the doubled 2000 population and projected 2100 population, the low estimate is the only one that is not at least doubled. None of the estimates in the graph supports a 400% increase.

 Low Estimate Middle Estimate High Estimate 2000 275,000,000 275,000,000 276,000,000 2100 283,000,000 571,000,000 1,182,000,000 Double the 2000 Population 550,000,000 550,000,000 550,000,000 400% Increase of the 2000 Population 1,375,000,000 1,375,000,000 1,380,000,000
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