Rounding digit
When rounding a decimal, the rounding digit is the digit in the last position you keep.
Repeating decimal
A decimal that has one or more digits that repeat forever.
Repeated solution
Multiple solutions for an equation are the same.
Remainder
If a divisor dies not divide a dividend evenly, the remainder is the whole number left over after the division.
Relation
Any set of ordered pairs.
Red herring
Unnecessary information in an applied problem.
Rectangular coordinate system
Formed by two real number lines intersecting at right angles.
Real part
The part of a complex number that is added to the imaginary part. $a$ in $a + bi$.
Real numbers
The numbers that you use in everyday life: $-1, 0, \frac{1}{2}, 3, …$.
Real number line
The diagram used to represent real numbers.