To find how many times higher the number of library visits before the examination day is compared to the average week, we can divide the two values:
- The number of visits one week before the examination: \( 2 \times 10^3 \)
- The average number of visits in a week: \( 5 \times 10^2 \)
Now, we divide the number of visits before the examination day by the average number of visits:
\[ \text{Ratio} = \frac{2 \times 10^3}{5 \times 10^2} \]
First, simplify the expression:
\[ \text{Ratio} = \frac{2}{5} \times \frac{10^3}{10^2} \]
Now calculate \( \frac{10^3}{10^2} = 10^{3-2} = 10^1 = 10 \).
So the ratio becomes:
\[ \text{Ratio} = \frac{2}{5} \times 10 \]
Now, calculate:
\[ \frac{2 \times 10}{5} = \frac{20}{5} = 4 \]
Therefore, the number of library visits one week before the examination day is 4 times higher than the average number of visits in a week. Thus, the final answer is:
\[ \boxed{4} \]