1. Teens
(1) Teens as sums with 10 / Sal looks at the 1 in each teen number and thinks about what it really means.
(2) Teen numbers: monkeys /Sal breaks the number 18 into 10 and 8.
2. Tens
(1) Intro to place value / Sal uses the number 37 to explain why we use a “ones place” and a “tens place” when writing numbers.
…every time you wanna know how many days its been to count it is a little bit painful. What if I were to group them into 10s.
Just by doing this very simple thing now all of a sudden it’s much easier to realize how many days have passed. You don’t have to count everything. You just have to say okay. One group of 10…
If we want to represent three 10s, we would have put a three in what we would call the 10s place. We’d put the seven in the ones place. And so how do you know which place is which? Well the first place starting from the right, the first place is the ones place.
(2) Place value example: 25 / Sal shows 25 as 2 tens and 5 ones.
(3) Place value example: 42 / Sal shows 42 as 4 tens and 2 ones.
3. Comparing 2-digit numbers
A lot of people might think when they see something like this that somehow equal means give me the answer. 1 plus 1 is the problem, equal means give me the answer.
That’s not what equal actually means. Equal is actually just trying to compare two quantities.
Now I will introduce you to other ways of comparing numbers. We’ll think about what we can do when we have different quantities on both sides.
Practice
- Comparing numbers (within 100) using the symbols <, >, and =. eg.: 19<91
- Order the numbers from least to greatest. eg.: 56 78 34 90
