Solve Vertical Subtraction: 19 minus 17 Step-by-Step

Q: Why do we start from the units column instead of the tens column?

We start from the right side (units) because if we need to borrow from the tens column, we must know that first! Starting left would mean we might change a digit we already used.

Q: What if the top digit is smaller than the bottom digit?

When the top digit is smaller, you need to borrow from the next column. For example, in 23 - 17, borrow 1 from the tens to make 3 become 13, then subtract: 13 - 7 = 6.

Q: How do I check if my subtraction is correct?

Use addition to check! Add your answer to the number you subtracted. If you get the original top number, you're correct. Here: 2 + 17 = 19 ✓

Q: What does the line under the numbers mean?

The line separates the problem from the answer. Everything above the line is what you're calculating, and you write your final answer below the line.

Vertical Subtraction with Two-Digit Numbers

$\begin{aligned} &19 \\ -& \\ &17 \\ &\underline{\phantom{776}} & \\ \end{aligned}$

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:00 Solve

00:03 Each time we calculate subtraction of 2 digits, and then we substitute

00:06 We'll start by subtracting ones from ones, and place in ones

00:12 Subtract tens from tens, and place in tens

00:19 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

$\begin{aligned} &19 \\ -& \\ &17 \\ &\underline{\phantom{776}} & \\ \end{aligned}$

Step-by-step solution

To solve this subtraction problem, follow these steps:

Step 1: Write the numbers vertically, aligning their digits properly. The problem is set up as follows:
$\begin{aligned} &19 \\ -& \\ &17 \\ \end{aligned}$
Step 2: Start with the units column. Subtract the digit 7 from the digit 9:
$9 - 7 = 2$
Step 3: Move to the tens column. Subtract the digit 1 from the digit 1:
$1 - 1 = 0$
Step 4: Combine the results from the tens and units columns. The complete calculation results in the number 2.

Therefore, the solution to the problem is $2$ .

Final Answer

Key Points to Remember

Essential concepts to master this topic

Column Alignment: Line up digits by place value for accurate subtraction
Right-to-Left Method: Start with units column: 9 - 7 = 2, then tens: 1 - 1 = 0
Check Work: Add your answer to the bottom number: 2 + 17 = 19 ✓

Common Mistakes

Avoid these frequent errors

Starting subtraction from the left side first
Don't subtract 1 - 1 first and then 9 - 7 = wrong order and confusion! This can lead to borrowing errors and incorrect final answers. Always start from the rightmost column (units) and work left toward the tens column.

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 do we start from the units column instead of the tens column?

We start from the right side (units) because if we need to borrow from the tens column, we must know that first! Starting left would mean we might change a digit we already used.

What if the top digit is smaller than the bottom digit?

When the top digit is smaller, you need to borrow from the next column. For example, in 23 - 17, borrow 1 from the tens to make 3 become 13, then subtract: 13 - 7 = 6.

How do I check if my subtraction is correct?

Use addition to check! Add your answer to the number you subtracted. If you get the original top number, you're correct. Here: 2 + 17 = 19 ✓

Do I need to write the 0 in the tens place?

In this problem, since 1 - 1 = 0 and it's the leftmost digit, we don't write the 0. The answer is simply 2, not 02.

What does the line under the numbers mean?

The line separates the problem from the answer. Everything above the line is what you're calculating, and you write your final answer below the line.

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