# Grade 2 & 3 Two digit number build

Number Sense for 2 and 3 digit number is no different than number sense for number to 10.

• Identify the quantity & Express multiple ways using place value units

words, multiplication units, expanded expressions, expander cards, blocks to 100 grids to number lines. STOP the pictures of tallies and circles. Build imagery that links to number so that students can use expressions. ADDITIVE COMPOSITION focus only on parts inside the whole to begin.

• Equal

record expressions and connect expressions multiple ways  Associative & Commutative Properties emerge

• Magnitude & Density

How close to? How far away from? Relate to other numbers.  Use referents of decades, (multiples of 5 & 10) , 50 and 100 and the language of more than, less than,  between, near, about. Stretch area models into number lines. COMPARE

• Inverses

understand the relationship and how to record it using the addition and the subtraction signs. Missing parts can be explained when you have solid number sense.  Relate using the grid and explaining the space. Relate using the number line and explaining the distances between.

### Build 2 & 3 digit with your students using the BERCS DECKS listed below.

The Two Digit Number and Three Digit Number books contain blackline masters and support pages that help you develop individual and whole class practice routines. They are ordered separately.  Just list what you want in an email to  glorway@thinking101.ca.

Decks are in colour and laminated. Your cost  \$12 per deck. The Two Digit Book is \$39.99 and the Three Digit Book is \$29.99.  I accept Visa, e transfer and school PO or personal cheques.

Get in the habit of building lists of expressions as students explain what they see, then encourage students to look for patterns in the lists so they are focused on organizing data.

I use this image to address misconceptions. Four on its own is misleading. Four ones is the place value notation. One fours is multiplication but not place value.

My dot collection materials include a variety of independent practice pages. Two Digit Number book in pdf is available by email: glorway@thinking101.ca \$35

The page below is meant to provide you guidance as you work with 2 digit number. There are several more pages of explanation here. HUNDRED GRID Hand out April 2018 .

It is part of a booklet of materials I am developing. Please respect my copyright and do not reproduce for others.. Thanks.

## NUMBER LINES MATTER

I move students between area models (grids) and number lines. The goal is to support them as they develop mental capacity for manipulating and managing number compositions in their mind’s eye. In other words, the goal is to move away from drawing and writing and toward efficiently expressing your thinking on paper. If you can add, use it to subtract. All you really need paper for is to make sure you do not lose track.

The number line is not magic nor is it worthy of special marks. It is a tool for developing a robust sense of number and accuracy with computations.