Answer:
Step-by-step explanation
Let's say d = distance, r = speed and t = time
We know the distance formula is :
distance = speed x time
d = r multiplied by t
d = rt
If the speed is 15km/hr, the time would be 30 minutes shorter.
Since d = rt,
90 = 15t
t = 6,
This means the time taken for the bus to complete the journey at 15km/hr would be 6hrs.
Originally though, the journey takes 30 minutes longer.
So we can say t = 6.5 hrs , and we know d = 90
Now we use the distance formula:
d = rt, since we want to find the original speed, we want to find r.
Speed = distance/time
r = d/t
r = 90/6.5
r = 180/13
Therefore the original speed is 180/13 km/hr
