The problem is to find the missing number in the equation: $2.5 \div \square = 0.025$. We need to determine the value that, when $2.5$ is divided by it, results in $0.025$.

1. Problem Description

The problem is to find the missing number in the equation: $2.5 \div \square = 0.025$. We need to determine the value that, when $2.5$ is divided by it, results in $0.025$.

2. Solution Steps

Let the missing number be $x$. The equation is:

$2.5 \div x = 0.025$

We can rewrite the division as a fraction:

$\frac{2.5}{x} = 0.025$

To solve for $x$, we can multiply both sides of the equation by $x$:

$2.5 = 0.025x$

Now, divide both sides by $0.025$:

$x = \frac{2.5}{0.025}$

To simplify the fraction, multiply both the numerator and denominator by 1000 to remove the decimal:

$x = \frac{2.5 \times 1000}{0.025 \times 1000} = \frac{2500}{25}$

Now, divide 2500 by 25:

$x = 100$

3. Final Answer

The missing number is 100.