11. It takes 10 hours to type 4 reports. How long will it take to type 15 reports?
A. 5 hours, 30 minutes
B. 6 hours
C. 37 hours, 30 minutes
D. 60 hours

Step 1 ：The problem is asking for the time it will take to type 15 reports given that it takes 10 hours to type 4 reports. This is a problem of proportionality.

Step 2 ：We can set up a proportion to solve this problem. The proportion is 4 reports : 10 hours = 15 reports : x hours.

Step 3 ：We can solve for x to find the time it will take to type 15 reports.

Step 4 ：Let's denote the number of reports as 'reports', the time it takes to type these reports as 'time', the target number of reports as 'target_reports', and the target time as 'target_time'.

Step 5 ：Given that 'reports' = 4, 'time' = 10, and 'target_reports' = 15, we can calculate 'target_time'.

Step 6 ：The calculation gives us that 'target_time' = 37.5. This means it will take 37.5 hours to type 15 reports.

Step 7 ：This matches with option C in the original question, which is 37 hours and 30 minutes.

Step 8 ：Final Answer: \(\boxed{C. 37 hours, 30 minutes}\)