Question

a long distance runner running a 5.0km track is pacing himself by running 4.5km at 9.0km/ hr and therest at 12.5km/hr. what is the average speed?​

Answer 1

Answer:-

Given:

Length of the track / total distance covered by the runner = 5 km.

Speed of the runner for first 4.5 km = 9 km/h

We know that,

Time = Distance/speed

So,

Time taken to travel first 4.5 km = 4.5 / 9

→ Time taken to travel first 4.5 km = 0.5 hrs.

Rest of the distance = 5.0 - 4.5 = 0.5 km

Speed of the runner for 0.5 km = 12.5 km/h

→ Time taken to travel 0.5 km = 0.5 / 12.5

→ Time taken to travel 0.5 km = 0.04 hrs

We know,

Average speed = Total Distance travelled/total Time taken

• Total distance travelled = 5 km

• Total Time = 0.5 + 0.04 = 0.54 hrs

→ Average speed of the runner = 5/0.54

→ Average speed of the runner = 9.25 km/h