Question

Prakhar goes from his home to school at a speed of 24 km/hr and returns at the speed of 36 km/hr. Find the average speed for the whole journey.

• A. 31.6 km/hr
• B. 2.8 km/hr
• C. 27.9 km/hr
• D. 26.3 km/hr

Answer 1

Answer:

B. 2.8 km/hr

This is a round trip, so distances are equal. Use the average speed formula for equal distances:

$\text{Average speed} = \frac{2ab}{a + b}$

Here, (a = 24), (b = 36)

$\text{Average speed} = \frac{2 \cdot 24 \cdot 36}{24 + 36}$

$= \frac{1728}{60} = 28.8$

Average speed = 28.8 km/h