What’s 18+18?

What’s 18+18?

The sum of 18 + 18 is equal to 36.

Addition of Whole Numbers

Addition is one of the most fundamental operations in arithmetic and math. It involves combining two numerical values together to arrive at a total sum. Beginning in elementary school, students learn to perform addition problems with larger and larger numbers.

By high school, students are fluent in adding numbers with multiple digits both mentally and using paper and pencil. However, going through the step-by-step process to add two numbers can still be helpful for practice and establishing foundational skills.

Let’s go through adding the numbers 18 and 18 together.

Writing the Addition Problem

The first step is writing the addition problem vertically with one number below the other:

18 +18

This lines up the ones and tens digits properly for easier addition.

Adding the Ones Digits

We start by adding the ones digit in each number, which is the rightmost digit:

18 +18

8 + 8 = 16

The ones digits are both 8, so 8 plus 8 equals 16. We write the 6 in the ones place and carry the 1 to add to the tens place in the next step.

Adding the Tens Digits

Now we add the tens digits, which are both 1. Additionally we need to add in the carry digit 1 from the previous step:

18 +18 36

1 + 1 + 1 (the carried 1) = 3

So the total in the tens place is 3, which we write down.

We don’t have any digits left to add. Since there is no carryover from the tens place, this completes the addition problem.

The total sum of 18 + 18 is 36.

Checking Our Work

To verify the answer, we can estimate that 18 + 18 should be around 36 since 20 + 20 = 40. Our actual sum of 36 seems reasonable compared to the estimate.

We could also add the numbers in reverse order and check that the total is the same:

18 +18 36

Getting the same sum regardless of order proves that 36 is the correct solution. Carrying out the addition process step-by-step helps build fluency and mastery of numerical addition.