Raj and Dev leave the school at 3:30 PM and cycle in opposite direction. If their speeds are 5km/hr and 7km/hr respectively, at what time they will be 18 km apart?

They will be 18 km apart at 5 pm.

Step-by-step explanation:

Speed of Raj is 5km/hr and speed of Dev is 7km/hr

Since they are going in opposite direction,

So, every 1 hours there difference will be (7 + 5) km = 12 km

Now, they will be apart 18 km distance 18/12 hours = 1 hour 30 min

The time will be 3:30 PM + 1 hour 30 min = 5 :00 PM

54 km / hours

step-by-step explanation:

we need to convert seconds to hours

60 seconds = 1 minutes

60 minutes = 1hour

15 m         60 second   60 minutes

  * *         = 54000 meters/ hour

second     1 minute             1 hour

now we need to convert meters to km

1000 m = 1 km

54000 m       1 km

*   = 54 km / hours

hour               1000m