the whole unit ( numbers to the left of the decimal will remain as the degrees:
270 will remain as degrees
now multiply the decimal by 60:
0.50 * 60 = 30 ( this becomes the minutes) if the answer had a decimal, you would multiply that decimal by 60 for the seconds, but since multiplying 0.50 by 60 was a whole number there are zero seconds
so the answer becomes 270 degrees 30 minutes and 0 seconds
which is written like: 270°30'0"