How do I tell wether a number is rational or irrational?

The best known irrational number is Pi, so, any formula with that in it it, like the formula for

circumference of a circle - Pi * D
area of a circle - Pi * R^2
volume of a sphere - 4/3 * Pi * R^3

Here D and R should be rational numbers, eg integers, to meet your definition.

No. In fact, there are many more irrational real numbers than there are rational real numbers.

It's a rational number since it can be represented as a ratio of two whole number, in this case 233 and 100.

All integers are rational numbers. The easiest way to see that is to write an integer as a fraction with 1 as a denominator; 4=4/1=8/2; 5=5/1.
Any number that can be written as a ratio of two integers numbers is by definition a rational number ( it is a ratio---rational).
Any decimal number with a periodic decimal part can be cast as a fraction, so it is rational.
An irrational number is a number that cannot be written as a fraction.
Examples: PI, sqRT(2), Sqrt(3), SQRT(5), e. There is an infinite number of them.

8.98=898/100
Both numerator and denominator are multiples of 2:The fraction can be simplified further. Simplifying, you get the irreducible form of the fraction as t 449/50.

False. A number is either rational or irrational; it cannot be both.

A rational number that can written as the RATIO of two whole numbers.
Examples:
1. Any whole number (-1, +13, -57) because they can be written as -1/1, 13/1 , -57/1.
2.Any number of the form a/b where a and be are integers (whole numbers) 1/3 , 17/(-9), 27/11, -17/9
13.572 572 572... where the sequence 572 (called the period) repeats for ever
-29.0123478478 478...
Numbers such as the square roots of numbers that are not perfect squares are not rational. They are irrational numbers. SQRT(2), SQRT(5), SQRT(6), SQRT(7), SQRT(8), SQRT(10), PI, e the base of natural logarithm, sin(22 degrees), cos(58),

Is the number 2 +
18 rational or irrational? rational
irrational Submit

They're all rational numbers since they can be expressed as the ratio of two whole numbers.

You're looking for a website with examples of rational and irrational numbers? Here's an extensive one:

1. Rational: Link
2. Irrational: Link

Or are you just asking for a few examples?

1. Rational: 5, 2/4, -34
   
2. Irrational: ?2, ?

Hope this helps!