## Key Concepts

• The counting numbers start with 1 and continue: $1,2,3,4,5\dots$.
• The whole numbers are the counting numbers and zero: $0,1,2,3,4,5\ldots$.
• When rounding numbers, look to the digit to the right of the place value to which the number should be rounded. If it is 5 or greater, increase the digit in the place value to which you are rounding by one and replace the position to the right with a zero. If 4 or less, do not change the place value to which you are rounding but do replace the position to the right with a zero.

## Key Equations

• Identity property of addition: $a+0=a$.
• Commutative property of addition: $a+b=b+a$.
• Identity property of multiplication: $a\cdot 1=a$.
• Commutative property of multiplication: $a\cdot b=b\cdot a$.
• Multiplication property of zero: $a\cdot 0=0$.
• Division properties of one: $a\div a=1$ and $a\div 1=a$.
• Division properties of zero: $0\div a=0$ and $a\div 0=\text{undefined}$..

## Glossary

difference
the result of subtracting
product
the result of multiplying
quotient
the result of dividing
rounding
to approximate the value of a number to a particular place value
sum