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Mental Math
How can Mental Math help you
solve equations?
What does it mean to do mental math?
Definition: Mental math: Calculations that are done in a student's head
without the guidance of pencil and paper, calculators or other aids.
Mental math is often used as a way to calculate and estimate quickly,
using math facts that a student has committed to memory, such as
multiplication, division or doubles facts.
Common Mental Math:
• Count on
• Doubles
• Friendly Numbers
• Front-End Adding or
Expanded Notation
Count On:
If one of the numbers being
added is a small number,
then just count on..
8 + 4 =
4 is a small number,
so just count on
to get your answer.
Count On:
RULE:
Usually, if one of the numbers
are from 1 to 5, you can just
count on.
Doubles:
Doubles are when you take a number and
add it to itself. Knowing your doubles
can help you solve equations quickly!
Examples: 2+2=
9+9=
15+15=
25+25=
You double the number.
Friendly Numbers:
A friendly number is a number that ends
with a “0”.When numbers have a “0” in
the ones spot; they are easier to add.
Example:
*to make 37 a friendly number,
I can add 3 to it
to make it 40
Examples:
*to make 45 a friendly number,
I can add 5 to it
to make 50
*to make 22 a friendly number,
I can subtract 2 from it
to make 20
Friendly Numbers:
This is how friendly numbers help:
27 + 5=
If I make 27 into a 30,
30 + 2=
it is easier to solve
because I’m working with a
friendly number.
Friendly Number Equation:
Notice how I changed the equation to
30 + 2, NOT 10 + 5
Friendly Number Equation:
I had to manipulate the equation by subtracting
the (3) from the number being added (5) that I
moved to (27) to make (30).
Otherwise, I’m just make a new and different
equation that won’t give the same answer
Front-End Adding:
When you front-end add you use expanded
notation or your place values.
Expanded Notation is breaking your
number into ones, tens and hundreds
Eg. 58 42
5 tens, 8 ones 4 tens, 2 ones
50 + 8 40 + 2
Front-End Adding
• Front-end adding is when you start adding
from the left and move to the right
Eg.34 + 45
- start with the tens: 30 + 40 = 70
- now the ones: 4 + 5 = 9
Now you`re working with a friendly number
70 + 9 = 79
Front-End Adding
Let’s Review the Mental Math
Strategies
• Count on
• Doubles
• Friendly Numbers
• Front-End Adding or
Expanded Notation
Mental math

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Mental math

  • 2.
  • 3. How can Mental Math help you solve equations? What does it mean to do mental math? Definition: Mental math: Calculations that are done in a student's head without the guidance of pencil and paper, calculators or other aids. Mental math is often used as a way to calculate and estimate quickly, using math facts that a student has committed to memory, such as multiplication, division or doubles facts.
  • 4. Common Mental Math: • Count on • Doubles • Friendly Numbers • Front-End Adding or Expanded Notation
  • 5. Count On: If one of the numbers being added is a small number, then just count on.. 8 + 4 = 4 is a small number, so just count on to get your answer.
  • 6. Count On: RULE: Usually, if one of the numbers are from 1 to 5, you can just count on.
  • 7. Doubles: Doubles are when you take a number and add it to itself. Knowing your doubles can help you solve equations quickly! Examples: 2+2= 9+9= 15+15= 25+25= You double the number.
  • 8. Friendly Numbers: A friendly number is a number that ends with a “0”.When numbers have a “0” in the ones spot; they are easier to add. Example: *to make 37 a friendly number, I can add 3 to it to make it 40
  • 9. Examples: *to make 45 a friendly number, I can add 5 to it to make 50 *to make 22 a friendly number, I can subtract 2 from it to make 20 Friendly Numbers:
  • 10. This is how friendly numbers help: 27 + 5= If I make 27 into a 30, 30 + 2= it is easier to solve because I’m working with a friendly number. Friendly Number Equation:
  • 11. Notice how I changed the equation to 30 + 2, NOT 10 + 5 Friendly Number Equation: I had to manipulate the equation by subtracting the (3) from the number being added (5) that I moved to (27) to make (30). Otherwise, I’m just make a new and different equation that won’t give the same answer
  • 12. Front-End Adding: When you front-end add you use expanded notation or your place values.
  • 13. Expanded Notation is breaking your number into ones, tens and hundreds Eg. 58 42 5 tens, 8 ones 4 tens, 2 ones 50 + 8 40 + 2 Front-End Adding
  • 14. • Front-end adding is when you start adding from the left and move to the right Eg.34 + 45 - start with the tens: 30 + 40 = 70 - now the ones: 4 + 5 = 9 Now you`re working with a friendly number 70 + 9 = 79 Front-End Adding
  • 15. Let’s Review the Mental Math Strategies • Count on • Doubles • Friendly Numbers • Front-End Adding or Expanded Notation