Calculate the Sum: 173 + 18 Addition Problem

Q: Can I add from left to right instead?

It's much harder! Adding from right to left (ones, tens, hundreds) lets you handle carrying naturally. Left to right addition requires more mental math and is more error-prone.

Q: How can I check if my answer is right?

Try these methods:Subtraction check: 191 - 18 should equal 173Estimation: 170 + 20 = 190, so 191 makes senseAdd again: Redo the problem to confirm

Two-Digit Addition with Carrying

$\begin{aligned} &173 \\ +& \\ &~~18 \\ &\underline{\phantom{776}} & \\ \end{aligned}$

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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 the sum of 2 digits, and then we place

00:06 Let's start by adding ones with ones

00:09 Place the ones, and add 1 to the tens

00:18 Add tens with tens, remember to add 1 to the calculation

00:24 Place 0 in the missing digits

00:33 Add hundreds with hundreds, place in hundreds

00:36 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

$\begin{aligned} &173 \\ +& \\ &~~18 \\ &\underline{\phantom{776}} & \\ \end{aligned}$

Step-by-step solution

To solve this problem, we'll follow these steps:

Step 1: Align the numbers 173 and 18 by their rightmost digits. Write 173 above 18.
Step 2: Start adding from the ones column (rightmost). 3 (ones of 173) + 8 (ones of 18) = 11.
Step 3: Write down the 1 in the ones place and carry over the remaining 1 to the tens column.
Step 4: Move to the tens column. Add 7 (tens of 173) + 1 (tens of 18) = 8, plus the carried over 1 = 9.
Step 5: Write 9 in the tens place.
Step 6: Move to the hundreds column. Add 1 (hundreds of 173) with the carry, which is zero here, so it remains 1.

Therefore, the final sum of 173 and 18 is $191$ .

Final Answer

191

Key Points to Remember

Essential concepts to master this topic

Alignment: Line up digits by place value columns correctly
Technique: Start from ones: 3 + 8 = 11, write 1 carry 1
Check: Count up from 173: 174, 175... 191 confirms our answer ✓

Common Mistakes

Avoid these frequent errors

Forgetting to carry over when sum exceeds 9
Don't write 11 directly in the ones place = wrong answer like 17311! When any column sum is 10 or more, you must write only the ones digit and carry the tens digit to the next column. Always carry over when column sums exceed 9.

Practice Quiz

Test your knowledge with interactive questions

$\begin{aligned} &12 \\ +& \\ &~~2 \\ &\underline{\phantom{776}} & \\ \end{aligned}$

FAQ

Everything you need to know about this question

Why do I need to carry over the 1?

When adding in the ones column gives you 11, that means 1 ten and 1 one. The 1 ten belongs in the tens column, so you carry it over to add with the other tens digits!

What if I forget to add the carried number?

You'll get the wrong answer! In this problem, forgetting the carried 1 would give you 181 instead of 191. Always remember to add any carried digits to the next column.

How do I know which number goes on top?

It doesn't matter mathematically, but it's easier to put the larger number on top. This way, you're less likely to make alignment mistakes when the numbers have different lengths.

Can I add from left to right instead?

It's much harder! Adding from right to left (ones, tens, hundreds) lets you handle carrying naturally. Left to right addition requires more mental math and is more error-prone.

How can I check if my answer is right?

Try these methods:

Subtraction check: 191 - 18 should equal 173
Estimation: 170 + 20 = 190, so 191 makes sense
Add again: Redo the problem to confirm

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