When deciding between "a," "an," and "the" before "one rupee note," we need to consider how to correctly use articles in English:
1. Indefinite Articles ("a" and "an"):
- Use "a" before words that begin with a consonant sound.
- Use "an" before words that begin with a vowel sound.
2. Definite Article ("the"):
- Use "the" when referring to a specific item that is known to the reader/listener.
In this case, "one" begins with a vowel letter (o), but its pronunciation starts with a consonant sound (w). Therefore, we use the indefinite article "a" before it.
So the correct way to write the sentence is:
"It is a one rupee note."