Final answer:
The equivalent ratio when the warm-up time is 15 minutes is 1:15.
Step-by-step explanation:
To find the equivalent ratio when the warm-up time is 15 minutes, we need to determine the ratio in simplest form. Let's use the given options to find the equivalent ratio:
A. 1:15
B. 2:30
C. 3:45
D. 4:60
Since we want the ratio in simplest form, option D is the correct answer. We can simplify 4:60 by dividing both numbers by their greatest common factor. The greatest common factor of 4 and 60 is 4. Dividing both numbers by 4 gives us the simplified ratio of 1:15. Therefore, the equivalent ratio when the warm-up time is 15 minutes is 1:15.