- random number generators
- A device used to produce a selection of numbers in a fair manner, in no particular
order and with no favor being given to any numbers. Examples include dice, spinners,
coins, and computer programs designed to randomly pick numbers.
- range
- The range of a set of numbers is the largest value in the set minus the smallest value
in the set. Note that the range is a single number, not many numbers.
- ratio
- A rational number of the form a/b where a is called the numerator and b is called the denominator.
- range of the function f
- The set of all the numbers f(x) for x in the domain of f.
- ray
- A straight line that begins at a point and continues outward in one direction.
- real numbers
- Real numbers can be thought of as all the points falling along the number line in the coordinate plane.
- rectangle
- A parallelogram with four
right angles.
- recursion
- Given some starting information and a rule for how to use it to get new information, the rule is then repeated using the new information.
- reflect
- In a tessellation, reflect means to repeat an image by flipping it across a line so it appears as it would in a mirror.
- regular fractals
- see fractal.
- regular polygon
- A polygon whose side lengths are all the same and whose interior angle measures are all the same.
- relative frequency
- Relative frequency is the number of items of a certain type divided by the number of
all the numbers being considered.
- remainders
- After dividing one number by another, if any amount is left that does not divide evenly, that amount is called the remainder. For example, when 8 is divided by 3, three goes in to eight twice (making 6), and the remainder is 2. When dividing 9 by 3, there is no remainder, because 3 goes in to 9 exactly 3 times, with nothing left over.
- rhombus
- A parallelogram with four congruent sides.
- right angle
- An angle of 90 degrees.
- right triangle
- A triangle containing an angle of 90 degrees.
- rotate
- To rotate an object in a tessellation means to repeat the object by spinning it on a point a certain angle.
- rule of probabilities multiplication for simultaneous
independent events
- When finding the probability of two independent events (two things happening where the outcomes are not affected by each other), multiply the probabilities of each event happening to get the probability of both
events happening. For example, to find the probability of getting "heads" and then
"tails" when flipping a coin twice, multiply the probability of getting heads once by
the probability of getting tails once.
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