This document discusses strategies for mental math calculations without paper or calculators. It defines mental math as calculations done in the head using memorized math facts. It then describes common mental math strategies like count on, doubles, friendly numbers, and front-end adding or expanded notation. Count on involves counting up from the first number when adding a small single-digit number. Doubles uses knowing double facts like 2+2. Friendly numbers makes a number end in 0 to make adding easier. Front-end adding uses place value by starting with the tens and then ones place.

1. Mental Math

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