Complete Question:
A long distance runner running a 5.0km track is pacing himself by running 4.5km at 9.0km/hr and the rest at 12.5km/hr. What is the average speed?
Answer:
Average speed = 9.7333 km/h
Step-by-step explanation:
- Let the total distance be divided into A and B.
Given the following data;
- Total distance = 5 km
- Distance A = 4.5 km
- Speed A = 9.5 km/hr
- Speed B = 12.5 km/hr
To find the average speed;
First of all, we would determine the time taken to cover distance A in speed A by using the formula;
Substituting the values into the formula, we have;
Time A = 0.4737 hours
Total distance = distance A + distance B
5 = 4.5 + distance B
Distance B = 5 - 4.5
Distance B = 0.5 Km
Next, we would determine the time to cover distance B in speed B;
Time A = 0.04 hours
Total time = time A + time B
Total time = 0.4737 + 0.04
Total time = 0.5137 hours
Now, we would solve for the average speed;
Mathematically, the average speed of an object is given by the formula;
Average speed = 9.7333 km/h