# Math K-2

## Addition Strategies

These are 5 strategies primary students must know in order to have a solid mathematical foundation for intermediate level math to come.

**Tally Marks****:**Students draw the appropriate number of tally marks beside each added, grouping them in groups of five. To solve, they count them all together by 5s to get the total sum.

**Open Number Line:**Draw a number line that will encompass the addends and possible sum of the problem. Begin on the number line with the first addend, then hop the number of the second addend. The number landed on is the sum.

**Decomposing:**Decompose addends into tens and ones. For example, 35 would be written as 30 + 5, with the second decomposed addend written and lined up underneath the first. Add the ones, then add the tens. Add the total number of ones to the total number of tens to find the sum.

**Draw a Picture:**Students draw symbols, or some kind of pictorial representation of the addends, then count them all to get the sum.

**Counting Up:**Students begin with the largest addend (numbers) in their heads, then count up the number of the second addend to find the sum. For example, if adding 3 + 4, begin with 4, count up three times, and end up at 7. Another example is 29 + 3, begin with 29 and go 30, 31, 32.

For further explanation of the addition strategies, click the link below to view grade specific brochures.

#### Other Strategies Students Might Use

**Doubles:**There are five doubles students should memorize, these can then be used for a related fact and regrouping.

eg.,**5 + 5**= 10;**6 + 6**= 12;**7 + 7**= 14;**8 + 8**= 16;**9 + 9**= 18

**Related Fact:**Use a math fact they already know to solve a math fact they don't know

**Drawing Base Ten Blocks:**

eg., 7 + 6, use 6 + 6 = 12, so 7 + 6 = 13 (one more)

eg., 9 - 5, use 10 - 5 = 5, so 9 - 5 = 4 (one less)

**Regroup:**Redistribute the addition numbers

eg., 8 + 6

take one from the 8 and give it to the 6

8 + 6 = 7 + 7 = 14

## Subtraction Strategies

**Count Down:** If the number that is being subtracted is less than 5 have the student use the points on the number to aid them as they count down.

eg., 7 - 3 **touch** the pencil to the **7** and then **touch** each of the **points on the 3** as they count down:

**7 - 3 = 7**, 6, 5, **4**

**Magic Nine:** For subtracting 9s, use the magic nine trick which is to add the top two numbers together.

**Math Ladder:** For two-digit *(11-19)* minus one-digit numbers. Take the bottom number and subtract it from ten, then add it to the ones digit of the top number.

eg., 16 - 9 = (1 + 6) = 7

eg., 16 - 7 = (10 - 7 = **3**) + **6** = **9**

**Subtraction with Place Value Blocks:** Students draw flats, rods and ones cubes and trade to solve the problem.

See the brochure link below for a visual of how this is done.

Math ladder

subtraction with place value blocks

**Break Apart 1 or Both Numbers (Partial Differences**)

* eg. 76 - 28 Break apart 1 number into expanded place value form

(Break apart 28 into 20 + 8

(Break apart 8 into 6 + 2)

76 - 20 = 56

56 - 6 = 50

50 - 2 = 48

So 76 - 28 = 48