A motorcicle and a truck left the town at the same time .
After travelling in the same direction for 1 and a quarter hours , the motocicle had travelled 25 km farther than the truck . If the average speed of the motorcicle was 60 km/h find the average speed of the truck.
Let the speed of the motorcycle be M and that of the truck be T.
Now speed = distance / time and distance = speed * time.
After 1.25 hours the motorcycle had travelled 25 km more than the truck. We can write this as:
1.25*M = 1.25*T + 25
We are also given the average speed of the motorcycle as 60 km/h
=> 1.25*60 = 1.25*T + 25
=> 1.25*60 - 25 = 1.25*T
=> T = 50/ 1.25
=> T = 40 km/h
The average speed of the truck was 40 km/h
Since we know the average speed of the motorcycle and the time, we can compute the distance it had travelled.
We know that the distance is the product of the speed and time.
distance = speed*time
distance = 60(Km/hr)*1.25 hr
distance = 75 Km
We also know, from enunciation, that the motorcycle travelled 25 Km farther than the truck, after one and a quarter hours.
The distance travelled by the truck, after one and a quarter hours, is the difference between the distance travelled by the motorcycle and the amount of 25 Km.
distance = 75 - 25 = 50Km
Now, we can compute the average speed of the truck, since we know the distance travelled and the time:
av. speed of truck = distance/time
av. speed speed of truck = 50Km/1.25 hr
av. speed speed of truck = 40 Km/hr