A car travels 30km at a uniform speed of 40km/h and next 30 km at a uniform speed of 20km/h. find its average speed.

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Solution

Step 1: Given data:
Speed of the car for first $30km$ = $40 km/h$
Speed of the car for next $30km$ = $20 km/h$
Step 2: Calculation of the average speed of the car:
We know,
$A v e r a g e s p e e d = \frac{T o t a l d i s t a n c e t r a v e l l e d}{T o t a l t i m e t a k e n}$
Time taken to travel the first 30 Km = $\frac{30 k m}{40 km/h r} = 0.75 h r$
Time taken to travel the next 30 km = $\frac{30 k m}{20 k m / h r} = 1.5 h r$
Now,
Total distance travelled = $30km + 30km = 60 km$
Total time taken = $0.75hr + 1.5hr = 2.25 h r$
Thus,
$A v e r a g e s p e e d = \frac{60 k m}{2.25 h r}$
$A v e r a g e s p e e d = 26.66 k m h^{- 1}$
Hence,
The average speed of the car is $26.66 k m h^{- 1}$ .

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