Terry Tortoise and Rabby Rabbit are best friends. Their home is 150 km apart. One day, they decided to meet. So Terry and Rabby started walking and running respectively towards each other at uniform speed at 9 am and they meet each other at 3:48 pm in the afternoon. Rabby runs at a speed 24 km/hr and stopped to take a nap after every 12 km He takes a nap for 15 minutes. Had Rabby made the journey without taking rest, they would have met 108 minutes earlier.

Question

anonymous · Answer

what would be the speed of Rabby after taking nap, is it 18 km/hr

anonymous · Answer

he runs 12 km in the first half an hour and then rests for 15 minutes. so after the rest he has run 12 km in 45 mins so his speed for first 12 km  = 12 / 3/4 = 16 km / hr.

is that what u want?

anonymous · Answer

hi, yes, so his speed would now be 16 km/hr? right

anonymous · Answer

yes - his average speed over the first 45 minutes is 16 km / hour. when he starts running again it will be at 24 km/hr again

anonymous · Answer

Also, cannt it be considered, as every 15 mintues he runs 6 km/hr

anonymous · Answer

so in 1 hour it comes to 18 km/hr

anonymous · Answer

15 minutes rest considered

anonymous · Answer

no - you cannot add speeds because speed is a ratio:  distance / time. you have to consider the total distance and the changed time (in this case the time has changed). It is valid to add distances and times but not speeds. People often fall into this trap.