Subtract 18 from 100: Column Method Step-by-Step

Q: Why can't I just subtract 8 from 0 in the ones place?

You cannot subtract a larger number from a smaller one in subtraction! When the top digit is smaller, you must borrow from the next column to make it bigger.

Q: What happens when the tens place is also 0?

Keep borrowing! Go to the hundreds place, borrow 1 (making it 0), which gives the tens place 10. Then borrow 1 from tens (making it 9) to give ones place 10.

Q: How do I remember the borrowing steps?

Think of it like breaking a bigger bill: 1 hundred becomes 10 tens, then 1 ten becomes 10 ones. You're just changing the form of the same amount!

Q: Why is my answer 92 instead of 82?

You probably forgot to reduce the hundreds digit after borrowing! When you borrow 1 from the hundreds place (1), it must become 0, not stay as 1.

Q: Can I check my subtraction answer?

Yes! Add your answer to the number you subtracted: $ 82 + 18 = 100 $. If you get the original number, your subtraction is correct!

Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Solve

00:03 Each time consider borrowing 2 digits, and then we'll place

00:06 0 is less than 8

00:09 The tens digit is also equal to 0 so we can't borrow from it

00:13 We'll borrow one hundred from the hundreds for the tens

00:17 So now instead of 0 we'll have 10, in the tens place!

00:20 And now we'll borrow ten from the tens for the ones

00:23 Which will turn the tens from 10 to 9

00:28 So now instead of 0 we'll have 10, in the ones place!

00:32 Now subtract ones from ones, and place in ones

00:40 Subtract tens from tens, and place in tens

00:44 Place 0 in the borrowed digits

00:47 Subtract hundreds from hundreds, and place in hundreds

00:50 And that's the solution to the problem

Step-by-step written solution

Follow each step carefully to understand the complete solution

1

Understand the problem

$\begin{aligned} &100 \\ -& \\ &~~18 \\ &\underline{\phantom{776}} & \\ \end{aligned}$

2

Step-by-step solution

To solve the problem $100 - 18$ , we'll perform the subtraction using borrowing:

Step 1: Arrange the numbers vertically:
$\begin{aligned} & 100 \\ - & \\ & ~~18 \\ & \underline{\phantom{776}} \end{aligned}$
Step 2: Start subtracting from the rightmost digit (the units place). Subtract 8 from 0. Since 0 is smaller than 8, we need to borrow.
Step 3: Borrow from the tens place. The tens place is also 0, so we must continue to the hundreds place. Borrow 1 from the hundreds place, turning it from 1 to 0, and making the tens place 10.
Step 4: Now we have 10 in the tens place. Borrow 1 from this new tens digit, turning it from 10 to 9, and giving the units place 10.
Step 5: Subtract 8 from 10 in the units place. This gives us 2.
Step 6: Move to the tens place. Subtract 1 from 9, which gives us 8.
Step 7: As there's nothing left to subtract in the hundreds place, we are left with 0.
Step 8: Combine the results to form the final answer: 82.

Therefore, the solution to the subtraction problem is $82$ .

3

Final Answer

82

Key Points to Remember

Essential concepts to master this topic

Rule: Borrow from the next higher place when needed
Technique: Convert 100 to 10 tens, then 9 tens + 10 ones
Check: Add the answer back: 82 + 18 = 100 ✓

Common Mistakes

Avoid these frequent errors

Forgetting to reduce the borrowed-from digit
Don't borrow from the hundreds place and leave it as 1 = incorrect answer 92! When you borrow 1 from hundreds, it becomes 0, not stays 1. Always reduce the digit you borrowed from by 1.

Practice Quiz

Test your knowledge with interactive questions

$\begin{aligned} &105 \\ -& \\ &~~~~3 \\ &\underline{\phantom{776}} & \\ \end{aligned}$

FAQ

Everything you need to know about this question

Why can't I just subtract 8 from 0 in the ones place?

+

You cannot subtract a larger number from a smaller one in subtraction! When the top digit is smaller, you must borrow from the next column to make it bigger.

What happens when the tens place is also 0?

+

Keep borrowing! Go to the hundreds place, borrow 1 (making it 0), which gives the tens place 10. Then borrow 1 from tens (making it 9) to give ones place 10.

How do I remember the borrowing steps?

+

Think of it like breaking a bigger bill: 1 hundred becomes 10 tens, then 1 ten becomes 10 ones. You're just changing the form of the same amount!

Why is my answer 92 instead of 82?

+

You probably forgot to reduce the hundreds digit after borrowing! When you borrow 1 from the hundreds place (1), it must become 0, not stay as 1.

Can I check my subtraction answer?

+

Yes! Add your answer to the number you subtracted: $82 + 18 = 100$ . If you get the original number, your subtraction is correct!

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Subtract 18 from 100: Column Method Step-by-Step

Column Subtraction with Borrowing Process

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