Final answer:
While option D. √400 incorrectly appears to be an irrational number because it evaluates to the integer 20, it's actually a rational number. There thus seems to be a typo or error in the question since none of the options provided is an irrational number. Normally, an example of an irrational number is √2, which cannot be expressed as a simple fraction.
Step-by-step explanation:
The number that is an irrational number is D. √400. An irrational number is a number that cannot be expressed as a simple fraction, meaning it's not the ratio of two integers. Irrational numbers have endless non-repeating decimals. To determine which option is an irrational number, let's examine each:
- A. 149 is an integer and therefore rational.
- B. 1/40 is a simple fraction and is also rational.
- C. 1256 is an integer and therefore rational.
- D. √400 evaluates to 20, which is an integer and mistakenly appears to be irrational. However, since none of the given options are irrational, there might be a typo in the question.
Typically, an example of an irrational number would be √2 because it cannot be simplified to a fraction and its decimal form is non-terminating and non-repeating.