Subtraction with Blocks: Calculate 72 - 45 Using Visual Decomposition

To solve this problem, we'll perform a simple subtraction:

• Step 1: Identify the given numbers: Total blocks = 72, Blocks to remove = 45.
• Step 2: Subtract the number of blocks being removed from the total number of blocks.

Let's perform the subtraction step-by-step:

$72 - 45$

First, subtract the units digit: $2 - 5$.

Since 2 is smaller than 5, we need to borrow from the tens column:

• Borrow 1 ten from the 7 (in 72), making it 6.
• The units now become 12.

Now subtract the units digits: $12 - 5 = 7$.

Next, subtract the tens digits: $6 - 4 = 2$.

Combine the results to get the number remaining:

The number of blocks remaining after removing 45 from 72 is $27$.

This matches the correct choice among the provided answers, which is option 3: $27$.

Therefore, the solution to the problem is $27$.