Add multi-digit whole numbers including using a standard algorithm with procedural fluency.
Recall addition facts with sums to 20 with automaticity.
Identify the number that is ten more and one hundred more than a given three-digit number.
Compose and decompose three-digit numbers in multiple ways using hundreds, tens and ones. Demonstrate each composition or decomposition with objects, drawings and expressions or equations.
Addition with the standard method is the goal, but students may need to spend time with base 10 blocks before they are ready for this step.
First, addd the ones' digits 3 + 9. Since 3 + 9 is 12, which is 2 ones and 1 ten, we write the 1 above the tens' digits.
Next, add the tens' digits together, remembering to add in the 1 ten that we made in the first step. We are adding 5 tens + 8 tens + 1 ten, which gives us 14 tens. 14 tens is the same as 4 tens and 1 hundred, so we write a 1 above the hundreds' place.
Finally, add the hundreds together. 1 + 2 + 3 = 6 hundreds.
The grouping method may look convoluted, but it is actually the method most of us use if we are mentally adding numbers together. Some students are much stronger in mental arithmetic strategies, so they prefer to rely on the grouping method to add numbers.
In this method, think of each number, decomposed into its hundreds, tens, and ones.
Group together the hundreds, the tens, and the ones in both numbers.
Add like place values together to get your final answer.
How do these methods work? Both rely on an understanding of place value. Some students will need to use hands-on manipulatives (place value blocks) in order to be able to efficiently learn addition. They may need to use these blocks for several weeks in order to solve the problems, but they will eventually be able to solve them without using the blocks!
Click here for an animation of how place value blocks can be used to help students understand addition. Note: This animation may be too small to be clearly seen on a phone. The image changes approximately every 10 seconds.