The following strategies are used in the classroom and are endorsed by our math mentors and school district to improve math skills.
Basic Math Facts:
We are continually working on mastering our math facts through daily quizzes and at any time that the occasion arises.
I am frequently reminding the students to use their "doubling strategy".
Doubling Strategy with "x2", "x4", and "x8":
Ex.: "2 x ___" or " ___ x 2"
2 x 7 = ___ or 7 x 2 = ___
Think: 2 is "1 x 2", so "2x7 or 7x2" is 7 doubled which gives 14. So the product (le produit) of 2x7 or 7x2 is 14.
Ex.: "4 x ___" or " ___ x 4"
4 x 3 = ___ or 3 x 4 = ___
Think: 4 is "2 x 2", so "4x3 or 3x4" is 3 doubled twice like this:
3x2=6 and 6 doubled is 12. So the product (le produit)
of 4x3 or 3x4 is 12.
Ex.: "8 x ___" or "___ x 8"
8 x 7 = ___ or 7 x 8 = ___
Think: 8 is "2x2x2" , so "8x7 or 7x8" is 7 doubled three times like this:
7x2=14 and 14x2=28 and 28x2=56. So the product (le produit) of 8x7 or 7x8 is 56.
Multiplying by 10
5 x 10 = _____ or 10 x 5 = ______
Think: 5 groups of ten
10 10 10 10 10
So, 5 x 10 is the same as 50.
When multiplying larger numbers by 10, you may decompose (break apart) the larger number.
For example:
65 x 10
Think: 60 x 10 and 5 x 10
6 groups of ten is 60.
So, 60 groups of ten is 600. And 5 groups of ten is 50.
600 + 50 is the same as 650
Multiplying by 5
Use the strategy for multiplying by 10 and then take half of that answer (product). This strategy works because 5 is half of ten.
For example:
5 x 6 = _______
Think 10 x 6 is the same as 60.
Half of 60 is 30.
So, 5 x 6 is equal to 30.
Multiplying by 9
9 x 6 = ?
Multiply by 10, then subtract one group of the number that you are multiplying by 9.
Think: 10 groups of 6 is 60
And 60 – 6 is 54
When multiplying larger numbers:
Example: 16 x 9 or 9 x 16
16 x 10 = 160
160 - 16 = 144
or
Decompose larger number : 16 is the same as 10 + 6
10 x 9 = 90
6 x 9 = 54
90 + 54 = 144
Multiplying by 3
When multiplying by 3, double the number and add one extra group of that number.
8 x 3
Think: Double 8 2 x 8 is 16
Add on a group of 8 16 + 8 is 24
So 8 x 3 = 24
For larger numbers:
14 x 3 or 3 x 14
2 x 14 = 28
28 + 14 = 42
or
14 is the same as 10 + 4
10 x 3 = 30
4 x 3 = 1230 + 12 = 42
Multiplying by 6
Use the strategy for multiplying by 3 and double the answer
6 x 7
Think: 3 x 7 = 21
So, 6 x 7 = 42
For larger numbers, use decomposition:
24 x 6
24 is the same as 20 + 4
20 x 6 = 120
4 x 6 =24
120 + 24 = 144
Basic Math Facts:
We are continually working on mastering our math facts through daily quizzes and at any time that the occasion arises.
I am frequently reminding the students to use their "doubling strategy".
Doubling Strategy with "x2", "x4", and "x8":
Ex.: "2 x ___" or " ___ x 2"
2 x 7 = ___ or 7 x 2 = ___
Think: 2 is "1 x 2", so "2x7 or 7x2" is 7 doubled which gives 14. So the product (le produit) of 2x7 or 7x2 is 14.
Ex.: "4 x ___" or " ___ x 4"
4 x 3 = ___ or 3 x 4 = ___
Think: 4 is "2 x 2", so "4x3 or 3x4" is 3 doubled twice like this:
3x2=6 and 6 doubled is 12. So the product (le produit)
of 4x3 or 3x4 is 12.
Ex.: "8 x ___" or "___ x 8"
8 x 7 = ___ or 7 x 8 = ___
Think: 8 is "2x2x2" , so "8x7 or 7x8" is 7 doubled three times like this:
7x2=14 and 14x2=28 and 28x2=56. So the product (le produit) of 8x7 or 7x8 is 56.
Multiplying by 10
5 x 10 = _____ or 10 x 5 = ______
Think: 5 groups of ten
10 10 10 10 10
So, 5 x 10 is the same as 50.
When multiplying larger numbers by 10, you may decompose (break apart) the larger number.
For example:
65 x 10
Think: 60 x 10 and 5 x 10
6 groups of ten is 60.
So, 60 groups of ten is 600. And 5 groups of ten is 50.
600 + 50 is the same as 650
Multiplying by 5
Use the strategy for multiplying by 10 and then take half of that answer (product). This strategy works because 5 is half of ten.
For example:
5 x 6 = _______
Think 10 x 6 is the same as 60.
Half of 60 is 30.
So, 5 x 6 is equal to 30.
Multiplying by 9
9 x 6 = ?
Multiply by 10, then subtract one group of the number that you are multiplying by 9.
Think: 10 groups of 6 is 60
And 60 – 6 is 54
When multiplying larger numbers:
Example: 16 x 9 or 9 x 16
16 x 10 = 160
160 - 16 = 144
or
Decompose larger number : 16 is the same as 10 + 6
10 x 9 = 90
6 x 9 = 54
90 + 54 = 144
Multiplying by 3
When multiplying by 3, double the number and add one extra group of that number.
8 x 3
Think: Double 8 2 x 8 is 16
Add on a group of 8 16 + 8 is 24
So 8 x 3 = 24
For larger numbers:
14 x 3 or 3 x 14
2 x 14 = 28
28 + 14 = 42
or
14 is the same as 10 + 4
10 x 3 = 30
4 x 3 = 1230 + 12 = 42
Multiplying by 6
Use the strategy for multiplying by 3 and double the answer
6 x 7
Think: 3 x 7 = 21
So, 6 x 7 = 42
For larger numbers, use decomposition:
24 x 6
24 is the same as 20 + 4
20 x 6 = 120
4 x 6 =24
120 + 24 = 144