A car travelled 2 hours at 60 km/h and 100 km at 40 km/h. Please calculate the average speed of the car. Show your calculations (including the data, formulas, result and unit).

Answer 1

To calculate the average speed of the car, we first need to determine the total distance traveled and the total time taken.

Step 1: Calculate the distances

1. Distance covered in the first part:

   • Speed = 60 km/h
   • Time = 2 hours \[ \text{Distance}_1 = \text{Speed} \times \text{Time} = 60 , \text{km/h} \times 2 , \text{h} = 120 , \text{km} \]

2. Distance covered in the second part:

   • Distance = 100 km (given)

Step 2: Calculate the total distance

\[ \text{Total Distance} = \text{Distance}_1 + \text{Distance}_2 = 120 , \text{km} + 100 , \text{km} = 220 , \text{km} \]

Step 3: Calculate the total time

1. Time taken for the first part: 2 hours (already given)
2. Time taken for the second part:
   • Distance = 100 km
   • Speed = 40 km/h \[ \text{Time}_2 = \frac{\text{Distance}}{\text{Speed}} = \frac{100 , \text{km}}{40 , \text{km/h}} = 2.5 , \text{h} \]

Step 4: Calculate the total time

\[ \text{Total Time} = \text{Time}_1 + \text{Time}_2 = 2 , \text{h} + 2.5 , \text{h} = 4.5 , \text{h} \]

Step 5: Calculate the average speed

The average speed is calculated using the formula: \[ \text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}} \] \[ \text{Average Speed} = \frac{220 , \text{km}}{4.5 , \text{h}} \approx 48.89 , \text{km/h} \]

Result

The average speed of the car is approximately 48.89 km/h.