Subtract 4 from 72: Base-10 Block Decomposition Problem

Subtraction with Base-10 Block Representation

If we have 72 blocks in total and we remove 4 of those blocks, how many blocks remain? Remember you can break down a row of 10 blocks into single units.

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Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

If we have 72 blocks in total and we remove 4 of those blocks, how many blocks remain? Remember you can break down a row of 10 blocks into single units.

2

Step-by-step solution

To solve this problem, we will perform a simple subtraction of the number of removed blocks from the total number of blocks.

  • Step 1: Identify the total number of blocks and the blocks removed.
  • Step 2: Use the formula for subtraction to determine the remaining blocks: Remaining blocks=Initial blocksRemoved blocks \text{Remaining blocks} = \text{Initial blocks} - \text{Removed blocks} .
  • Step 3: Perform the calculation.

Now, let's work through each step:

Step 1: We start with 72 72 blocks and remove 4 4 blocks.

Step 2: Using the subtraction formula mentioned, we compute:
724=68 72 - 4 = 68 .

Step 3: Therefore, after removing 4 blocks, the number of blocks that remain is 68 68 .

Thus, the solution to the problem is 68\mathbf{68}.

3

Final Answer

68 68

Key Points to Remember

Essential concepts to master this topic
  • Subtraction Rule: Total blocks minus removed blocks equals remaining blocks
  • Visual Method: Count 7 tens + 2 ones = 72, then subtract 4
  • Check: Verify 68+4=72 68 + 4 = 72 matches original amount ✓

Common Mistakes

Avoid these frequent errors
  • Confusing addition and subtraction operations
    Don't add the removed blocks to the total = 76! This gives you more blocks than you started with, which is impossible when removing blocks. Always subtract: 72 - 4 = 68.

Practice Quiz

Test your knowledge with interactive questions

If we have 85 blocks in total, how many blocks will remain if we remove 4 tens and 1 one?

FAQ

Everything you need to know about this question

Why do we use base-10 blocks for this problem?

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Base-10 blocks help visualize the numbers! You can see 72 as 7 long strips (tens) plus 2 individual blocks (ones). This makes subtraction easier to understand.

What if I need to break apart a ten-block?

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Great question! If you need to subtract more ones than you have, you can break apart one ten-block into 10 individual blocks. This is called regrouping or borrowing.

How do I know which operation to use?

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Look for key words: 'remove', 'take away', or 'subtract' mean use subtraction. The problem says 'remove 4 blocks', so we subtract!

Can I solve this without the blocks diagram?

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Absolutely! You can solve 724=68 72 - 4 = 68 directly. The blocks just help you visualize what's happening with the numbers.

What's the easiest way to check my answer?

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Use addition to check subtraction! If 72 - 4 = 68, then 68 + 4 should equal 72. Since it does, your answer is correct!

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