Add two-digit numbers | Year 3 Mathematics PDF Download

How can we show addition?

There are various methods to illustrate addition.
Consider this calculation: 43 + 32
We can demonstrate this using both a part-whole model and a bar model.
In the part-whole model and bar model representations, 43 + 32 = 75
Each method shows the equation as parts (43 and 32) adding up to the whole number (75).

Understanding the Calculation

When a number consists of multiple digits, a place value chart with headings such as ones, tens, hundreds, and thousands helps to understand the value of each digit.
Let's consider the calculation 25 + 33.
Using a place value chart, we break down each number into its tens and ones components.
For 25, which has 2 tens and 5 ones, we add 2 packets of pencils to the tens column and 5 marbles to the ones column.
Now, adding the second number to the place value chart:
33 has 3 tens and 3 ones, so we add 3 packets of pencils to the tens column and 3 marbles to the ones column.

Next, starting with the ones column, we count everything to find the answer to the calculation.
In the place value chart, there are 8 marbles in the ones column and 5 sets of pencils in the tens column.
Therefore, 25 + 33 = 58.

Solved Examples

Example 1: In this part-whole model, we are working out the whole number for the calculation 18 + 11.
The part-whole model shows 18 + 11 as:
18 + 11
Using a place value chart to calculate:
We represent 18 with 1 set of pencils (tens) and 8 marbles (ones) on top. For 11, we represent it with 1 set of pencils (tens) underneath and 1 marble (ones).
Adding up the ones column first, we count a total of 9 ones.
In the tens column, there are 2 tens.
Therefore, 18 + 11 = 29.

Example 2: Here is a bar model made up of the parts 32 and 26.
This is the same as 32 + 26.

Here is 32 + 26 in a place value chart.
There are 8 ones and 5 tens.
32 + 26 = 58
When you're working out additions using these methods, always add up the numbers in the ones column first.