Six-mile radius or six-miles' radius????
locations within a __________ radius of London’s Charing Cross railway station.
A) six- mile
B) six miles'
Tell me, please, which option is correct and why. I thought "six mile" was wrong but my teacher told me it was the right answer. And I wanna hear from the native speaker which one is really correct!)

Question

Six-mile radius or six-miles' radius????
locations within a __________ radius of London’s Charing Cross railway station.
A) six- mile 
B) six miles' 
Tell me, please, which option is correct and why. I thought "six mile" was wrong but my teacher told me it was the right answer. And I wanna hear from the native speaker which one is really correct!)

Answer

Correction:  "I wanna hear" is not standard written English.  Use "I want to hear."

"six-mile" radius is the answer for English exams.

The basic rule is to hypenate when a modifier refers to another modifier.
This is an expensive, old car.  (expensive modifies car and old modifies car)
This is a 50-year-old car.  (neither 50 nor year modify car)

More information here:
https://www.quickanddirtytips.com/education/grammar/stacked-modifiers

Answer

definitely six mile radius
No need for the apostrophe.

Answer

Hi Olena. The 'six-mile' is acting as an adjective in this sentence. We don't make adjectives plural in English.  It was a difficult 26-mile race. -- Both difficult and 26-mile are describing race, so both will remain singular. Hope this helps, Ellen

لا تفوّت فرصة تعلّم لغة جديدة وأنت مرتاح في منزلك. تصفّح مجموعتنا المختارة من مدرّسي اللغات ذوي الخبرة وسجّل في درسك الأول الآن!