A woman travelled at a speed of 20 m/min for 90 min, and at a speed of 55 m/min for 60 min. Her average speed (in m/min) for the entire journey is:
- AOption (a)
34
- BOption (b)
27
- COption (c)
40
- DOption (d)
38
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Correct answer
34
Why this answer is correct
Shortcut Trick
Time ratio = 90 : 60 = 3 : 2
⇒ Average speed = (20 × 3 + 55 × 2) ÷ (3 + 2)
⇒ = (60 + 110) ÷ 5 = 170 ÷ 5 = 34
∴ Answer = 34 m/min
Alternate Method
Given:
⇒ Speed1 = 20 m/min, Time1 = 90 min
⇒ Speed2 = 55 m/min, Time2 = 60 min
Formula:
⇒ Average Speed = Total Distance ÷ Total Time
Calculations:
⇒ Distance1 = 20 × 90 = 1800 m
⇒ Distance2 = 55 × 60 = 3300 m
⇒ Total Distance = 1800 + 3300 = 5100 m
⇒ Total Time = 90 + 60 = 150 min
⇒ Average Speed = 5100 ÷ 150 = 34 m/min
Final Answer: 34 m/min
Additional Information
1. Average Speed (Different Times): When time is different, use weighted average → (v1t1 + v2t2) ÷ (t1 + t2)
2. Average Speed (Equal Distances): Use harmonic mean → 2v1v2 ÷ (v1 + v2)
3. Shortcut Concept: If time ratio is given, multiply speeds with time ratio directly


