Adding Four Two-Digit Numbers

Learn how to add four two-digit numbers by breaking the work into smaller, easier steps.

Reading is good — doing is better. Practice Adding Four Two-Digit Numbers as an interactive lesson.

Definition

Adding four two-digit numbers means finding the total when you combine four numbers that each have a tens digit and a ones digit, like 12, 25, 34, and 18. Instead of trying to add all four at once, we add two numbers at a time, working left to right or by finding friendly pairs first.

Remember the rule

Add two numbers first, then add the third, then add the fourth — one step at a time!

Key words

Two-digit number: A number with two places: a tens place and a ones place, like 23 or 47.
Sum: The answer you get when you add numbers together.
Ones place: The far-right digit in a number, which tells how many single units there are.
Tens place: The second digit from the right, which tells how many groups of ten there are.
Regrouping: When ones digits add up to 10 or more, you trade 10 ones for 1 ten and carry it over.
Friendly numbers: Numbers that are easy to add because they make a ten, like 13 and 17, which together make 30.
Column addition: Stacking numbers on top of each other and adding the ones column first, then the tens column.
Partial sum: The smaller total you get after adding just some of the numbers before finishing the whole problem.

Worked examples

11 + 22 + 13 + 14 = ?

→ 60 · Add left to right: 11+22=33, then 33+13=46, then 46+14=60. No regrouping needed!

15 + 25 + 30 + 20 = ?

→ 90 · Spot the friendly pair: 15+25=40, then 30+20=50, then 40+50=90.

18 + 12 + 27 + 33 = ?

→ 90 · 18+12=30 (friendly pair!), 27+33=60 (friendly pair!), then 30+60=90.

24 + 36 + 15 + 25 = ?

→ 100 · 24+36=60, 15+25=40, then 60+40=100. Looking for pairs that make round numbers helps a lot.

17 + 23 + 14 + 19 = ?

→ 73 · 17+23=40, 14+19=33, then 40+33=73. Check the ones column: 0+3=3, and tens: 4+3=7.

32 + 28 + 41 + 16 = ?

→ 117 · 32+28=60, 41+16=57, then 60+57=117. Remember to regroup: 0+7=7 ones, 6+5=11 tens, which is 1 hundred and 1 ten.

Common mistakes

Adding all four numbers at once in their heads without writing down the steps, which leads to losing track of the running total.
Forgetting to regroup (carry) when ones digits add up to 10 or more, causing the answer to be too small.
Adding the tens digits and ones digits in the wrong order, like adding tens before ones when doing column addition.
Skipping one of the four numbers by accident, especially when the numbers are written in a row.
Misreading a digit, like mixing up 16 and 61, which gives a totally wrong sum.

FAQs

Does it matter which two numbers I add first?

No! Addition can be done in any order and the answer stays the same. Pick whichever pair looks easiest, like numbers whose ones digits add up to 10.

What if the ones digits add up to more than 9?

That is called regrouping. Write down the ones digit of the sum and carry the tens digit over to the tens column to add there.

Can I add all four numbers in a column at once?

Yes! Stack all four numbers on top of each other, add the ones column first, regroup if needed, then add the tens column. It is a great method once you feel comfortable with regrouping.

How do I check my answer?

Add the four numbers again in a different order. If you get the same sum both times, you are most likely correct!

What are friendly number pairs and why should I look for them?

Friendly pairs are two numbers whose ones digits add up to exactly 10, like 13 and 17 or 22 and 28. They make a round number (like 30 or 50) that is much easier to work with.

My child gets confused keeping track of four numbers. Any tips?

Have your child circle or underline each number as they use it, and write the partial sum after each step. This way nothing gets skipped and the work is easy to check.

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