4rd grade math

Decimal notation for fractions

Ray
A ray has one endpoint where it starts and it extends forever on the other side.

Add mixed numbers

Comparing fractions

Proper fraction
Numerator is smaller than denominator
Improper fraction
Numerator is bigger than denominator.

Right triangle
A right triangle has one right angle.

Benchmark fractions
Fractions that are used frequently to do estimation.

Congruent shapes

Shapes are congruent when they have the same shape and size.

Common denominator
Multiples of 3 are 3, 6, 9, 12, 15, ...
Multiples of 4 are 4, 8, 12,16, ...
Common denominator is least common multiple or 12.

Line of symmetry

Protractor


A geometric tool used
to draw and measure angles

Arc

An arc is a part of a circle. The arc is shown in orange.

Algorithm for multiplication

Measure of an angle

The angle on the right measures 150 degrees

Tenth  and hundredth

Tenth: one of the equal parts when a whole is divided into 10 equal parts.

Hundredth: one of the equal parts when a whole is divided into 100 equal parts

Intersecting lines

Comparing decimals

Put the following decimal in order from greatest to least.
4.23    4.24    4.2    4.30    4.19

Answer :
4.30    4.24   4.23    4.20   4.19

Formulas
Area and perimeter of a rectangle

Area  = length x width

Perimeter = 2 x length + 2 x width

Circle
In a circle, you can put points anywhere on the purple arc. These points will be at the same distance from the fixed black point called center.

Tenths
The tenths place is shown in red. The 2 means that 2 parts are colored out of 10.

                      
                      8.29

Composite number
A number with more
than 2 factors. Factors
of 8 are 1, 2, 4, and 8.
8 is a composite number
since it has 4 factors
or 4 numbers than
can divide it evenly

                 
         

         12, 9 and 8          
         
                                      

Obtuse angle

An angle bigger than 90 degrees

Decimal

10.50      5.25      61.0     0.40       .333         

Number line
A straight line on which we put 0 and counting numbers

Reasonableness
There is no need to
do the math. Instead
use estimation to
eliminate answers that
are unreasonable.
50 times 30 = 1500,
therefore, the answer is 1551

             
       What is the product
            of 47  times  32?
            A. 4514    B. 1551
            C. 2947    D. 8114

Perimeter

Perimeter = 2 x length + 2 x width
                  =  2 x 6 + 2 x 2
                  =  12 + 4
                  = 16

Area          =  6 x 2 = 12

Solve an equation

  What is the value
  of b in the equation
   below?
   5 + b = 12
   Since 5 + 7 = 12,
    b = 7

1 ounce

• A slice of bread

• A CD without the case

• 2 or 3 strawberries depends on the size

Pattern:
What is the next
number in the list?

   12    15    18

Example of prime numbers
A prime number is a number
that has only 2 factors, 1
and the number itself.
7 is a prime number because
only 1 and 7 can be
multiplied to get 7

        
           
           5, 7, and 13            

Decimal point

The decimal point is the dot (.) separating the whole number from the fraction in the decimal notation.

Equivalent fractions