# Addition, Subtraction, Multiplication, and Division Strategies

**Addition Strategies:**

**Count All:**Count all of the objects in both numbers

**Count On:**Start with the bigger number and count on

**Doubles:**Adding a number with itself

**Doubles plus One:**Use your doubles facts and add 1 extra

"

(In 4+5 think of 5 as 4+1, so 4+5 is 4 doubled [8] plus 1)

**Monkey in the Middle"**or**doubles + 2**ex. 3 + 5 (when counting 3,**4**, 5) the number in the middle is doubled (4 +4)= 8(In 4+5 think of 5 as 4+1, so 4+5 is 4 doubled [8] plus 1)

**Add 9**: Start by adding 10, then just take 1 away

(For 8+9 start with 8+10 [18] and take away 1 to get 17)

**Add 10**: To add 10 you are putting 1 in the tens column

(7+10 starts with 0 tens,7 ones; We put 1 in the tens column [17])

**Subtraction Strategies:**

**Add Up:**Use addition to find the difference between numbers

**Subtract to 10s**: Subtract to get back to the nearest ten, then the rest

(82-5 : 82-2 gets you 80 then -3=77)

**Subtract to 100**: Subtract to get back to 100, then subtract the rest

(120-50 : 120-20 get you to 100, then -30 = 70)

**Multiplication Strategies:**

**G. E.T. Strategy= G**(roups)

**X E**(number in

**each**group) =

**T**(total)

**x 0:**The product will always be 0

**The product is the same as the factor being multiplied by 1**

x 1:

x 1:

**Just double the number that is being multiplied by 2 (use your doubles from addition)**

x 2:

x 2:

**Doubles plus one group (5x3 = 5x2 plus 5x1.**

x 3:

x 3:

**Double Double**

x 4:

x 4:

**(5x4 = 5x2x2. This is 5 doubled [10] and then double that answer to get 20)**

**Multiply by 10 and then cut it in half or skip count by 5's like on a clock.**

x 5:

x 5:

(6x5 = Start with 6x10 [60] and then just cut in half to get 30)

**Multiply by 3 and then just double**

x 6:

x 6:

(8x6 = Use your previous knowledge [8x3=24] and double the 24 to get 48)

**Partial products (using 5's) Multiply by 5, Multiply by 2 and combine**

x 7:

x 7:

**(8x7 = 8x5 [40] plus 8x2 [16] ; The final answer is 40+16, or 56)**

**Multiply by 4 and then just double (9x8 = 9x4x2. This is 9x4[36] doubled : 30 doubled=60 + 6 doubled=12, total is 72)**

x 8:

x 8:

**Multiply by 10 then take away a group (look for number patterns)**

x 9:

x 9:

**(9x3= 10x3 [30] take away a group of 3 [30-3] to get 27)**

**Product will end with a zero.**

x10:

x10:

**(8x10 = 8 groups of 10, or just 8 in the tens place followed by a 0, which is 80)**

**For single digits it's just a repeat digit**

x11:

x11:

(9x11=9x1 in the tens column [90] plus 9x1 in the ones column[9] or 9 shown twice [99] )

**Multiply by 10, Multiply by 2 and combine (look for a number pattern)**

x12:

x12:

(7x12 = 7x10 [70] plus 7x2 [14] for a total of 84 when you add the 70 and 14)

**Divison: (Using the inverse operation is a very efficient method that I would recommend trying first)**

**÷ 2:**Just split the number in half

(18 ÷ 2 is just 18 cut in half, which is 9)

**÷ 4:**Cut in half twice

(24÷ 2 is just 24 cut in half [12] then cut that in half to get 6)

**÷ 5:**Double then divide by 10 or use multiplication

(30÷ 5 is done by doubling the 30 [60] & dividing by 10,which removes the 0 ones [6] )

**÷ 6:**Cut in half, then divide by 3

(42÷6 is 42 cut in half [21] then divide that by 3 to get 7 )

**÷ 8**: Cut in half three times

(48 ÷ 6 is 48 cut in half [24] which gets cut in half [12] and one more time [6] )

**÷10:**Remove the 0 that is in the ones column

(90÷10 is done by deleting the 0 in 90 to get 9)