
Math Cheat Sheet (Kindergarten – 5th Grade)
Unless you’re an accountant, an engineer or a math teacher, you’ve probably forgotten the math lessons you learned in grade school.
Math at the elementary level revolves around learning conceptual frameworks and understanding patterns, in addition to the basic operations of addition, subtraction, multiplication and division. Younger students begin to understand basic amounts—whole, half and quarter—as they start to see math expand its significance beyond the classroom. Lessons that focus on estimation, inequalities and averages help your child begin to implement these lessons in the grocery store, on the baseball field and even at the dinner table.
If you can solve the problems below, you might be able to keep up with your child—and be a real help with arithmetic homework.
Estimation is the act of finding an approximate answer, not an exact answer.
To round off decimals:
 Find the place value you want (the "rounding digit") and look at the digit just to the right of it.
 If that digit is less than five, do not change the “rounding digit” but drop all digits to the right of it.
 If that digit is greater than or equal to five, add one to the “rounding digit” and drop all digits to the right of it.
To round off whole numbers:
 Find the place value you want (the "rounding digit") and look to the digit just to the right of it.
 If that digit is less than five, do not change the "rounding digit" but change all digits to the right of the "rounding digit" to zero.
 If that digit is greater than or equal to five, add one to the “rounding digit” and change all digits to the right of the rounding digit to zero.
Inequalities are mathematical expressions that show two quantities are not equal. An inequality is used when the exact value of an expression is unknown. Instead of an equals sign, use one of these symbols:
> greater than
< less than
≤ less than or equal to
≥ greater than or equal to
Mean, Median, Mode, Range
Consider the set of numbers: 80, 90, 90, 100, 85, 90.
The mean is another term for the average found by adding a set of numbers and dividing by the quantity of numbers there are in that set.
(80 + 90 + 90 + 100 + 85 + 90) / 6 = 89 1/6
The median is the number in the middle. To find the median, put the values in order from lowest to highest. Then find the number that is exactly in the middle.
80 85 90 90 90 100
If there is an even number of values, average the two values in the middle
90 + 90 / 2 = 90
Notice that there is exactly the same number of values above the median as below it.
The mode is the value that occurs most often.
90
The range is the difference between the lowest and highest values. The range shows how spread out the data are.
100  80 = 20
Shapes
Polygons are flat, closed figures with three or more sides. The most commonly recognized polygons are triangles, rectangles and squares. Here are a few terms that may have escaped your memory.
A quadrilateral, including squares and rectangles, has four sides.
A pentagon has five sides.
A hexagon has six.
An octagon has eight.
The number of sides also determines how many angles a polygon has. A quadrilateral has four angles, a pentagon has five, etc.
Prime Numbers
A prime number is a counting number that only has two factors—itself and one.
A composite number has more than two factors, such as six, whose factors are 1, 2, 3 and 6.
The number one has only one factor (itself) and is neither prime nor composite.

