Second Grade Math: Place Value to Add and Subtract

While there are many different ways to teach children how to add and subtract, it is important for your child to understand the essence of each idea: Addition is “putting together” and subtraction is “taking apart.” It is also vital for your young learner to recognize the connection between the two operations — that they are the opposite of each other. 

Throughout your child’s learning of fact families (a set of related addition and subtraction or multiplication and division number equations), she will begin to see relationships between numbers, and become more confident with the idea of adding and subtracting.

During second grade, your child is introduced to the concept of using “place value” (the value of where the digit is in the number, based on the location of the digit) in order to add and subtract numbers. At this age, she will likely become stronger at taking numbers apart and putting them back together. This strategy helps her think abstractly about what she is doing while building her number-sense at the same time. The idea of regrouping and memorizing steps is not the focus. Students often begin to feel more confident about what they are learning and their own understanding. 

Another way to think about this strategy is the idea of “break apart.” We are breaking the numbers apart — adding or subtracting — then putting them back together. This can be done several ways and with any model or tool necessary. The idea is to move your child toward doing most of the math work in her head, so that as she gets older, her mental math skills grow stronger.

Here are some examples of the break apart method:

23 + 75 =                                                      

1. Think about the value of each digit in each number. 
2. 23 is made up of 20 and 3
3. 75 is made up of 70 and 5
4. Combine the tens (20 + 70 = 90)
5. Combine the ones (3 + 5 = 8)
6. 90 + 8 = 98
7. So 23 + 75 = 98

98 – 47 =

1. 90 – 40 = 50
2. 8 – 7 = 1
3. 50 + 1 = 51

Image courtesy of University Place Primary School

Image courtesy of CCES 2nd Grade Math Resources

Here is a printable for your child to try. Think outside the box and use place value to help him add and subtract the different numbers. Have fun!

What are your favorite strategies to explain second grade math concepts to your child? Share them on the Scholastic Parents Facebook page!

Feature Photo Courtesy © J2R/Thinkstock