Question

If a car travels a distance at a speed of 18 km/hr and comes back the same distance at 30 km/hr. What is the average speed (In km/hr) for the total journey?
1. 25
2. 21.5
3. 22.5
4. 24

Answer 1

Correct Answer - Option 3 : 22.5

Given:

Speed while going = 18 km/hr

Speed while returning = 30 km/hr

Formula used:

Average speed for same distance = 2ab/(a + b)

Where, a = speed while going

B = speed while returning

Calculation:

Average speed = 2ab/(a + b)

⇒ 2 × 18 × 30/(18 + 30)

⇒ (36 × 30)/48

⇒ 90/4

⇒ 22.5 km/hr

∴ The average speed for the whole journey is 22.5 km/hr