Question

Correct the Sentences : 01}She is a ten-years old girl .

Answer 1

She is a ten-year old girl .

Answer 2

The correct sentence here would be, 'She is a ten-year-old girl.'

• Instead of using 'ten-years' here, we use ten-year instead because when we are writing anyone's age we hyphenate their age when the age is acting as a noun and when the age is an adjective that comes before the noun and subsequently modifies the noun.  
• Here 'ten-year-old' is acting as an adjective that describes the noun and hence it has to be hyphenated.