In Grade 2 we make sense of number to 100. To do that well, students must trust five, trust ten and learn to collect and trust units of ten without counting each ten. Three tens = 3(10) = 3 sets of ten = thirty. We know 10 + 10 + 10 = 30 but we will only use that information when stuck.

Remember my goals are: explaining reasoning and problem solving being flexible and confident in working with numbers knowing how to prove you are correct Knowing how to double check your work Being able to use mental connections to solve problems Standing on your own two feet as a thinker Understanding number relationships and properties Not just knowing the answer but knowing it IS the ANSWER.

I use the phrase NUMBER IS IN NUMBER...... Always be thinking about ways to take apart in equal groups first. “counting by” fives and tens are foundational sequences that must have meaning. Students need to see the fives accumulating as they count. Recording decades with a five in them with the expansion cards helps bring meaning to the notation.

We are going to translate the block numberline into a hundred grid model to see how the fives are embedded in the tens.

We have already proved this is one hundred by filling it two directions with the tens.

Unsnap the next five and place in the grid.

Unsnap the next five and place in the grid. 10 20 30 40 50 5

Unsnap the next five and place in the grid. 20 30 40 50 10

Unsnap the next five and place in the grid. 20 30 40 50 60 15

Unsnap the next five and place in the grid. 30 40 50 60 20

Unsnap the next five and place in the grid. 30 40 50 60 70 2 5

Unsnap the next five and place in the grid. 40 50 60 70 80 30

Unsnap the next five and place in the grid. 40 50 60 70 80 3 5

Unsnap the next five and place in the grid. 50 60 70 80 90 40

Unsnap the next five and place in the grid. 50 60 70 80 90 45

Unsnap the next five and place in the grid. 60 70 80 90 100 50

Unsnap the next five and place in the grid. 60 70 80 90 100 55

Unsnap the next five and place in the grid. 70 80 90 100 60

Unsnap the next five and place in the grid. 70 80 90 100 65

Unsnap the next five and place in the grid. 80 90 100 70

Unsnap the next five and place in the grid. 80 90 100 75

Unsnap the next five and place in the grid. 90 100 80

Unsnap the next five and place in the grid. 90 100 85

Unsnap the next five and place in the grid. 100 90

Unsnap the next five and place in the grid. 100 95

100

Using the models what would 45 look like? Describe it to someone. How many fives? How many tens? Place it on the numberline and explain why it goes there.

0 10 20 30 40 50 60 70 80 90 100 Where would 45 sit? Worksheet.

Students need lots of practice. They should: given a two digit number orally or in writing Build the 2 digit number, or describe what it would look like with the models, 65 would be 6 tens and a five or 3 tens, 3 tens and a 5 or 5 tens that’s fifty and one more ten and a five Explain it by shading in on the hundred grid, by demonstrating where it sits on a numberline and by constructing with place value cards. Represent as standard and expanded notation (list multiple ways to describe) Describe with flexible place values referring to the grid, the blocks or the numberline Place it on a given numberline that has other numbers already identified. (between 60 and 70, between 64 and 69, after 64, before 66 etc.) Place it in order when given a written set of two digit numbers. Words and numbers. Worksheet.

Use the flashmath powerpoint to practice identifying and naming the counting by fives and tens sequence. After you name the number with tens and ones, take it apart different ways.

Remember my goals are: explaining reasoning and problem solving being flexible and confident in working with numbers knowing how to prove you are correct Knowing how to double check your work Being able to use mental connections to solve problems Standing on your own two feet as a thinker Understanding number relationships and properties Not just knowing the answer but knowing it IS the ANSWER.