Join 60,000+ competitive exam aspirants
or with email
Your Cart
Subtotal₹0
Total₹0
Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
Join 60,000+ competitive exam aspirants
If a person covers 90 km at a speed of 45 km/h and another distance of 150 km at a speed of 50 km/h, then his average speed for the whole journey is:
46 km/h
48 km/h
49 km/h
47 km/h
48 km/h
Calculate individual times (t1=90/45=2 h, t2=150/50=3 h), sum the distances (240 km), and divide by the sum of times (5 h).
Distance 1 (d1) = 90 km, Speed 1 (v1) = 45 km/h. Distance 2 (d2) = 150 km, Speed 2 (v2) = 50 km/h.
Average Speed=TotalTimeTotalDistance=v1d1+v2d2d1+d2
Calculate individual times (t1=90/45=2 h, t2=150/50=3 h), sum the distances (240 km), and divide by the sum of times (5 h).
Many students incorrectly calculate the average of the two speeds (45+50)/2=47.5 km/h, which is mathematically invalid for varying distances.
Calculate the time for each segment
Time is equal to distance divided by speed. For the first segment: t1=4590=2 h. For the second segment: t2=50150=3 h.
t1=2 h,t2=3 h
Calculate total distance and total time
Total distance D=90+150=240 km. Total time T=2+3=5 h.
D=240 km,T=5 h
Find the average speed
Average speed = Total distance divided by total time: 240/5=48 km/h.
Average Speed=5240=48 km/h
B is correct because the total distance of 240 km divided by the total time of 5 hours results in an average speed of 48 km/h.
This concept frequently appears in competitive exams where motion problems involve multiple segments with different velocities; always find total distance and total time first.
Get instant step-by-step AI explanations, full shift Previous Year Papers (SSC GD, RRB, SSC JE), and regional rank analysis on the official Examoogle App.
Free Download • 100K+ Aspirants