Adding Three Numbers Worksheets

About adding three numbers

Adding three numbers teaches children that they can add in any order, and it is a great place to use strategies: look for pairs that make 10 or doubles first. In grade 1, children add three whole numbers whose sum is 20 or less; in grade 2 they add up to four 2-digit numbers.

Strategies for three addends

• Make 10 first: 6 + 5 + 4 is easier as (6 + 4) + 5 = 15.
• Doubles first: 3 + 7 + 3 is (3 + 3) + 7 = 13.
• Columns: for 2-digit numbers, add all the ones, carry if needed, then add all the tens.

Adding three numbers worksheets: what is in the set

There are 5 adding three numbers worksheets on this page, and each one has an answer key. The first two use single-digit numbers, so children can practice the strategies, and the last three use 2-digit numbers in columns, with a grid paper version for children who need to keep the digits in line:

The worksheets follow the Common Core standard for adding three whole numbers in grade 1 (1.OA.A.2) and the one for adding up to four 2-digit numbers in grade 2 (2.NBT.B.6). The Common Core standards for grade 1 operations and algebraic thinking and the Common Core standards for grade 2 number and operations in base ten describe both.

Adding three numbers: how many different problems are there?

There are 1,000 ordered ways to choose three digits from 0 to 9, and 220 different ones when the order does not count. When children are adding three numbers, the total of the three digits is anywhere from 0 to 27. This table shows how those 1,000 triples divide:

Grade 1 children add three numbers whose sum is 20 or less, which covers 92% of the triples. The most common sums of three digits are 13 and 14, with 75 triples each. Of the 1,000 triples, 244 (24%) contain two digits that make 10, and 280 (28%) contain a double, so the two main strategies for adding three numbers apply to most problems.

3 addends worksheets: choosing the best strategy

The skill in adding three numbers is to look at all three before adding. This table shows 12 problems with the strategy that works best for each one, using the rule that children should first look for a pair that makes 10, then for a double, and then add the biggest numbers first:

The strategies work because addition can be done in any order, a fact known as the associative property and the commutative property. See the page on making 10 for the pairs that make 10, and the doubles and near doubles page for doubles.

Wikipedia’s article on addition describes the properties in more detail.

Column addition with three addends: how big can the carry be?

When two numbers are added in a column, the carry is 0 or 1. With three addends, it can be 0, 1 or 2, because three digits add up to at most 27. Here is how the ones-column carries divide for three random 2-digit numbers:

78% of the problems carry 1 or 2, so children must be ready to carry a 2. That is the new idea in column addition with three addends, and the worksheets include problems that need it. The size of the answer is also bigger than with two numbers:

Most sums of three 2-digit numbers have three digits, so the answer line must be long enough. The grid paper worksheet leaves a box for the hundreds digit.

Adding four numbers: carries of 3

When adding four numbers, the ones column can add up to 36, so the carry can be as big as 3. The worksheet for four 2-digit numbers makes children carry 0, 1, 2 or 3 in the ones column, and the shares are:

The sums of four 2-digit numbers are also larger. About 63% of the sums are 200 or more:

Column addition with three addends: 10 practice problems with answers

These ten problems show the working for column addition with three addends, with the carry in its own column. A teacher can cover the last two columns and let children solve each problem, then check the working:

Common mistakes when adding three numbers

Most mistakes come from a small number of causes. This table shows the wrong answers that come from three typical errors, so a teacher can see which one a child is making:

A child who leaves out the third number has not read the whole problem, and a child who carries 1 when the carry is 2 has probably added the digits in pairs. Writing the carry in a box above the tens column helps with both.

Adding 3 numbers worksheets: a guide for parents and teachers

Adding 3 numbers worksheets are best used after a child can add two numbers within 20 with confidence. Start with the single-digit sheets, and keep the first sessions short, about 10 minutes. Ask the child to say out loud which two numbers they are adding first and why, because the habit of looking before adding is the main goal of the lesson. Move to the column worksheets only when the child can add three single-digit numbers without counting on their fingers. The answer key on the last page of each PDF lets children check their own work.

Adding three numbers up to 20: every sum with an example

In grade 1, the three numbers add up to 20 or less. This table shows how many different triples of the digits 1 to 9 there are for each sum from 3 to 20, with one example:

The sums from 10 to 13 have the most triples, so these are the problems that children meet most often. Sums near 3 or 20 are rare.

Three numbers that make 10

When adding three numbers that make 10 there are only 8 different triples, and each one can be solved by making a smaller ten. This is a good first set of facts to memorize, because they appear again and again in other problems:

Adding three numbers in your head: look for round numbers

With bigger numbers, a child can add three numbers in their head if two of them make a round number. Look for pairs that end in 5 and 5, or in numbers that add up to 10, and add those first:

Adding three numbers word problems

Word problems show that adding three numbers happens in real life, such as when we add up the parts of a collection or the scores in a game. Ask children to write the number sentence first and to say what the answer counts:

A five-day plan for adding three numbers

Most children in grades 1 and 2 need about a week of short sessions for adding three numbers. This plan goes from the strategies to column addition:

When a child can add three numbers, the next step is 2-digit addition with regrouping, which uses the same carrying. The whole sequence is on the addition worksheets page.