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For 1st grade math, I am using Mammoth Math Light Blue Series. I like mammoth math for a lot of reasons. It is an open-an-go type of curriculum, it is sufficiently challenging, and one of the most affordable homeschool options available. CLICK HERE to read my full review of homeschool math curricula. The downloadable version of Mammoth Math can be printed and used with all of your children. I use Mammoth Math as the base math curriculum for my children starting in first grade. Like any curriculum, some children will need extra practice and different instructional approaches for some concepts. Extra practice using visuals and manipulatives can help children better understand math concepts, including 2-Digit Place Value.
Mammoth Math becomes even more affordable when you buy it at a discount. I purchased my PDF version through Homeschool Buyer’s Co-op, a company that negotiates discounts on popular homeschool curricula. It is free to join. The co-op charges a minimal fee (usually around $1) when you buy a curriculum through them. Homeschool Buyers Co-op has Mammoth Math available at a discount (I was able to get around 40% off) several times through out the year. CLICK HERE to join Homeschool Buyer’s Co-op.
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Teaching 2-Digit Number Sense and Place Value
The last few weeks, we have been working on the 2-digit Numbers and Place Value Unit (from Mammoth Math Light Blue Series 1-A work text). We have already done a lot of work with an abacus. THIS ABACUS is my favorite as it splits the 10s into groups of 5 by the colored beads. This feature makes it easier to see what the different numbers look like and how they break apart into smaller chunks. Even with all of the abacus work, my 1st grader is still struggling with number sense and place value for 2-digit numbers.
It is time to approach the instruction in a new way. Additional manipulatives and visuals can be used to help teach this concept. I have some base-10 blocks on order, but am using my set of Cuisenaire Rods until they arrive.
- 3×5 index cards
- Base-10 blocks or Cusinaire Rods
- Paper or dry erase board
On 3×5 cards, write out the numbers 10, 20, 30, 40, ….up to 90. Cut five blank 3×5 cards in half and write the numbers 1 to 9.
On a piece of paper, dry erase board, or large index card, make a place to put tens blocks and ones blocks.
Since my children have only been using Cuisenaire Rods for a couple of weeks, I made a key so they could easily find the number they needed by color.
Procedure for Teaching 2-Digit Place Value and Number Sense:
Write out a 2-digit number. In my child’s Mammoth Math lesson, she was supposed to break a 2-digit number apart in an additional sentence by tens and ones. So for her activity, I wrote 52 with an addition sentence (see photo to left).
Then, I had my child make 52 using Cuisenaire Rods. Five orange 10-rods go on the tens side of the card. The two rod goes on the ones side. If you are using base-10 blocks, two single blocks would go on the ones side.
Next, I had my child find the 50 card (to represent the 5 tens) and the 2 card (to represent the 2 ones). I demonstrated how to make 52 by placing the 2 card in the ones place on the 50 card.
Lastly, I demonstrated how to pull the cards apart to show 50 plus 2 is 52.
We then repeated this procedure with a variety of 2-digit numbers. We will be practicing this concept frequently to help solidify concepts of place value and number sense for 2-digit numbers. Once she understands the concept, we will move back to the Mammoth Math worksheets.
These cards can also be used to demonstrate adding ones to numbers ending in zero.
Teaching 2-Digit Place Value and Number Sense using the Number Cards with an Abacus:
Teaching concepts using a variety of visuals and manipulatives can help children maintain interest in learning math concepts and also help them generalize concepts.
The same cards can also be used with an abacus. First the child makes 30 on the abacus and puts up the 30 card.
Next, the child adds 4 more and puts up the 4 card.
Lastly, the child puts the 4 card on top of the ones place on the 30 card to show that 30 plus 4 is 34.
Summary on Teaching 2-Digit Place Value and Number Sense
Whatever math curriculum or teaching approach is used, some children may need additional practice with manipulatives and visuals to understand the concept being taught. An abacus, Cuisenaire Rods, and Base-10 blocks can all be used to help a child develop number sense and learn the concept of place value.
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