How many minutes pass from the middle of the first quarter of an hour to the middle of its third quarter?

Let’s convert hours to minutes:
1 h = 60 min.
In one quarter of an hour in total:
60/4 = 15 minutes
First quarter – from 1 to 15 minutes.
The second – from 16 to 30 minutes.
The third – from 31 to 45 minutes.
The fourth – from 46 to 60 minutes.
The middle of the first quarter is equal to:
15/2 = 7.5 minutes
The middle of the third quarter is equal to:
45/2 = 22.5 minutes
The difference between them is:
22.5-7.5 = 15 minutes
Answer: 15 minutes.