While covering a distance of 39 km, a man noticed that after cycling for 5 hours 5 minutes, the distance covered by him was of the remaining distance. What was his speed (in km/hr, rounded off to one decimal place)?
- AOption (a)
6.5
- BOption (b)
3.2
- COption (c)
1.9
- DOption (d)
4.3
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Correct answer
4.3
Why this answer is correct
Shortcut Trick
Total distance = 39 km. Ratio of Covered Distance to Remaining Distance = 5 : 4.
Total units = 5 + 4 = 9 units → 39 km. Covered distance = (5/9) × 39 = 21.666 km.
Time taken = 5 hours 5 minutes = 5 + 5/60 = 5 + 1/12 = 61/12 hours.
Speed = Distance ÷ Time = 21.666 ÷ (61/12) ≈ 4.26 km/hr.
∴ The correct answer is 4.3 km/hr.
Alternate Method
Given: Total distance = 39 km, Time = 5 hours 5 minutes, Covered distance = 5/4 × Remaining distance.
Let the remaining distance be x km.
⇒ Covered distance = 5x/4 km.
⇒ Total Distance = 5x/4 + x = 9x/4
⇒ 9x/4 = 39
⇒ x = (39 × 4) ÷ 9 = 156/9 = 52/3 km.
⇒ Covered Distance = 39 − 52/3 = (117 − 52)/3 = 65/3 km.
⇒ Time = 5 hours + 5/60 hours = 305/60 = 61/12 hours.
⇒ Speed = Distance ÷ Time = (65/3) ÷ (61/12) = (65/3) × (12/61) = 260/61 km/hr.
⇒ Speed ≈ 4.262 km/hr ≈ 4.3 km/hr.
∴ The correct answer is 4.3 km/hr.
Additional Information
Speed, Distance, and Time Relationship
The basic formula is Speed = Distance ÷ Time. Ensure all units are consistent (e.g., km and hours) before calculation.
Unit Conversion
To convert minutes to hours, divide by 60. To convert km/hr to m/s, multiply by 5/18.
Rounding Off Rules
If the second decimal digit is 5 or more, increase the first decimal digit by 1. Here, 4.26 becomes 4.3.