Answer: 3 days
Explanation;
First, let's calculate the total distance you run each day.
Distance per lap = 400 meters
Laps per day = 10
Total distance per day = Distance per lap × Laps per day
Total distance per day = 400 meters × 10 = 4,000 meters
Now we need to find out how many days it would take to run a total of 12 kilometers (12,000 meters).
Total distance desired = 12,000 meters
Number of days = Total distance desired / Total distance per day
Number of days = 12,000 meters / 4,000 meters
Number of days = 3
So, it would take you 3 days to run a total of 12 kilometers if you run 10 laps of 400 meters each day.