In 2013 , the estimated world population was 7.1 billion. Use a doubling time of 66 years to predict the population in 2026, 2054, and 2111.

What will the population be in $2026?$
The population will be $◻$ billion.
(Round to one decimal place as needed.)

Step 1 ：The question is asking for the estimated world population in 2026, given that the population was 7.1 billion in 2013 and that the population doubles every 66 years.

Step 2 ：To solve this, we can use the formula for exponential growth, which is: $P=P0\times (2{)}^{t/T}$ where: $P$ is the final population, $P0$ is the initial population, $t$ is the time elapsed, and $T$ is the doubling time.

Step 3 ：In this case, $P0$ is 7.1 billion, $t$ is 2026 - 2013 = 13 years, and $T$ is 66 years.

Step 4 ：We can plug these values into the formula to find the estimated population in 2026.

Step 5 ：Let's calculate this: $P0=7.1$, $t=13$, $T=66$, $P=P0\times (2{)}^{t/T}=8.138645569020689$

Step 6 ：The estimated world population in 2026 is approximately 8.14 billion.

Step 7 ：Final Answer: The population will be $\boxed{{\displaystyle 8.1}}$ billion.