Question

A, B & C are on a trip by a car. A drives during the first hour at an average speed of 50 km/hr. B drives during the next 2 hours at an average speed of 48 km/hr. C drives for the next 3 hours at an average speed of 52 km/hr. They reached their destination after exactly 6 hours. Their mean speed was:
1. 50 km/hr
2. \(50\dfrac{1}{3}\) km/hr
3. \(51\dfrac{1}{3}\)  km/hr
4. 52 km/hr 

Answer 1

Correct Answer - Option 2 : \(50\dfrac{1}{3}\) km/hr

Given:

Average speed of A = 50 km/hr

Average speed of B = 48 km/hr

Average speed of C = 52 km/hr

Formula used:

Distance = Speed × Time

Average speed = Total Distance/Total time

Calculation:

Distance covered by A in 1 hour = 50 km

Distance covered by B in 2 hours = 2 × 48

⇒ Distance covered by B in 2 hours = 96 km

Distance covered by C in 3 hours = 3 × 52

⇒ Distance covered by C in 3 hours = 156 km

Average speed = (50 + 96 + 156)/6

⇒ Average speed = 302/6

⇒ Average speed = \(50\dfrac{1}{3}\) km/hr

∴ The average speed of the car is \(50\dfrac{1}{3}\) km/hr.