Addition and Subtraction Review of Base-10 and Decomposing

Addition and Subtraction Review of Base-10 and Decomposing

Base 10 Blocks

Remember when you are modeling addition problems with base 10 blocks, you will model both problems. 100's to 100's , 10's to 10's, and 1's to 1's. Once you make a group of 10, you will need to regroup. The picture shows how this looks with base 10 blocks drawn.

Multiple Choice

Solve using base 10 blocks:

328 + 136

• 454

• 464

• 456

• 458

Base 10 Blocks Subtraction

Remember: When subtracting using base 10 blocks, you will only model the first number. You must follow the directions of the subtraction problem. You start with the first number and take away the second. You will also start in the lowest place value. Notice in the picture you may need to break up a 10 or a 100 in order to take away the correct number of 1's or 10's.

Adding with Decomposing

When adding using decomposing, you can decompose each addend into 100's, 10's, and 1's and then add. You will end up with several equations. Finally, you will add all of the sums together for the final answer.

Subtraction with Decomposing

Remember when you use decomposing with subtraction, you will only decompose the 2nd number. Keep the start number together! You will then decompose the 2nd number into parts to make the subtraction easier. Notice how you can take parts of the 10's and then you can take parts of the 1's away. Make sure the total amount you took away matches the problem!