Describe why pi is a real number but not a rational number

Pi is a real number because any number can be expressed in the form of (a+ib) where a is the real part and b is an imaginary part. its not a rational number because it cant be written as a fraction

Irrational numbers are numbers that can be written as decimals but not as fractions. ... Pi is an irrational number because it cannot be expressed as a ratio (fraction) of two integers: it has no exact decimal equivalent, although 3.1415926 is good enough for many applications.

Option (c) is the correct answer.

Explanation:

The bottom of pencil is placed at the starting point of scale. Whereas the tip of pencil depicts the end point of its length.

The bottom of pencil is at 0 mm and tip of pencil is at 18.73 mm. The appropriate amount of significant figures is 18.73 mm.

Therefore, we can conclude that out of the given options, pencil is 18.73 mm long.