To calculate the increase in the world’s population from 1500 CE to 2020, we subtract the population in 1500 CE from the population in 2020.
Given:
- Population in 1500 CE: \( 4.5 \times 10^8 \)
- Population in 2020: \( 7.8 \times 10^9 \)
Calculating the increase:
\[ \text{Increase} = \text{Population in 2020} - \text{Population in 1500 CE} \]
First, we need to express both populations in the same order of magnitude. We can convert \( 4.5 \times 10^8 \) to be in terms of \( 10^9 \):
\[ 4.5 \times 10^8 = 0.45 \times 10^9 \]
Now, substituting back into the increase calculation:
\[ \text{Increase} = 7.8 \times 10^9 - 0.45 \times 10^9 \]
Combining these:
\[ \text{Increase} = (7.8 - 0.45) \times 10^9 = 7.35 \times 10^9 \]
Therefore, the world's population increased by \( \mathbf{7.35 \times 10^9} \).