Solve the Addition Equation: Finding the Missing Number in 24 + □ = 45

To solve the equation $24 + \Box = 45$ using two jumps on a number line, we will take the following approach:

• Step 1: Make the first jump from 24 to the closest higher round number, which is 30.
• Step 2: Calculate how much is needed to reach from 30 to 45.
• Finally, we combine the lengths of the two jumps to find $\Box$.

Now, let's calculate each step:

Step 1: The first jump from 24 to 30 is 6 units.

Step 2: From 30 to 45, the jump is 15 units.

Adding these two jumps: $6 + 15 = 21$.

Therefore, the number that completes the equation $24 + \Box = 45$ is $21$.