Question

A car travels 30 km at a uniform speed of 40 km per hour and the next 30 km at a uniform speed of 60 km per hour. Find it's average speed.

Answer 1

Here's the Solution :

Let the average speed of the Car be x

We know that

s = d/t

=>t1 = d/s

=> t1= 30km/40km/h

=> t1 = (3/4) h

And

t2 = 30km/60km/h

=> t2 =( 1/2 ) h

Now ,

speed = distance / time

=> x = (30km + 30km)/ (t1 + t2)

=> x = 60 km /( 3/4 + 1/2)h

=> x = 60 km / (3+2)/4 h

=> x = 60 km / 5/4 h

=> x = 60 km × 4 / 5h

=> x = 12 × 4 km/h

=> x = 48 km/h

Required speed is 48 km/h

Answer 2

Answer: 48km/h

Explanation:

1. As you know, Distance = Speed ×Time, so Time = Distance/Speed

2. For first 30 km, time is 30/40 as 30km by 40km/h speed

3. For next 30 km, time is 30/60 as you know...

4. REMEMBER, Avg. speed = Total distance/ Total time

5. Total distance will be 60km and total time will be 30/40 + 30/ 60 ...

6. On putting values, you will get Answer = 48km/h

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