A woman drives a car. During her journey, she travels 20 minutes at a speed of 60 km/hr, another 30 minutes at a speed of 40 km/hr and 1 hour at a speed of 50 km/hr. The average speed of the car is:

Given:

The first 20 speed of woman = 60 km/hr

The next 30 minutes speed of the woman = 40 km/hr

The next 1 hours the speed of woman = 50 km/hr

Formula used:

\(Average\ speed\ ={Total\ distance\over Total\ time }\)

Calculation:

Let the average speed be X

According to the question

⇒ The distance covered by woman in 20 minutes = \({20\over60}× 60 = 20\ km\)

⇒ The distance covered by woman in 30 minutes = \({30\over60}× 40=20\ km\)

⇒ The distance covered by woman in 1 hours = 50 × 1 = 50 km

The total distance = 20 + 20 + 50 = 90 km

The total time = 20 min + 30 min + 60 min = 110 min = \({110\over60}\ hours\)

The average speed = \({90\over{110\over60}}={540\over11}\ km/hr\)

∴ The required result will be \({540\over11}\ km/hr\).