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Mental math

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.

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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