Irrational numbers are numbers that cannot be expressed as a simple fraction, meaning they cannot be written as the ratio of two integers. They have non-repeating, non-terminating decimal expansions.
From your list, the only irrational number is:
- π (pi), which is approximately 3.14159... and continues without repeating.
The other numbers are:
- 0.285714... (this is a repeating decimal, and it can be expressed as a fraction, so it is rational).
- 2/7 (this is a fraction, and therefore rational).
- 0.28 (this is a terminating decimal and can be expressed as the fraction 28/100, so it is rational).
- 0.28 (same as above, also rational).
Thus, the only irrational number in the list is:
- π