Mark and Susan start jogging from the same point. Mark jogs east at a speed of 6 km/h, while Susan jogs west at a speed of 4 km/h. If they start at 10:00 AM and stop when they have covered a total of 20 km, at what time will they stop?



Answer :

To determine the time when Mark and Susan will stop jogging, let's go through the problem step by step:

### Step 1: Determine the relative speed of Mark and Susan
Since Mark is jogging east at 6 km/h and Susan is jogging west at 4 km/h, their relative speed is the sum of their individual speeds because they are moving in opposite directions.
- Relative speed = Speed of Mark + Speed of Susan
- Relative speed = 6 km/h + 4 km/h = 10 km/h

### Step 2: Calculate the total time taken to cover the distance
Next, we need to determine how long it will take for them to cover the total distance of 20 km when moving at a relative speed of 10 km/h.
- Time taken = Total distance / Relative speed
- Time taken = 20 km / 10 km/h = 2 hours

### Step 3: Determine the stopping time
Since they start jogging at 10:00 AM and it takes 2 hours to cover the distance, we add the time taken to the start time to find the stopping time.
- Start time = 10:00 AM
- Time taken = 2 hours
- Stopping time = 10:00 AM + 2 hours = 12:00 PM (noon)

### Step 4: Express the stopping time in hours and minutes
The stopping time is exactly 2 hours after 10:00 AM, which corresponds to 12:00 PM. This means:
- Stopping time (hours) = 12 hours
- Stopping time (minutes) = 0 minutes

Therefore, Mark and Susan will stop jogging at 12:00 PM (noon).