A motorboat rows 16 km/h in still water and the speed of the river current is 4 km/h. Find the time taken to row 80 km downstream. MCQ with Answer and Explanation

A motorboat rows 16 km/h in still water and the speed of the river current is 4 km/h. Find the time taken to row 80 km downstream.
A. 4.0 hours
B. 3.5 hours
C. 4.5 hours
D. 5.0 hours
Answer: Option A
Solution (By JKSSB Mock Tests)
Downstream speed = 16 + 4 = 20 km/h. Time taken = 80 / 20 = 4 hours.

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Practice More Time Speed and Distance Questions

Question #1
A sound wave travels at a speed of 330 m/s. If the echo of a sound is heard from a wall after 2 seconds, find the distance of the wall from the source.
A. 660 meters
B. 600 meters
C. 300 meters
D. 330 meters

Correct Answer: Option D


Explanation:
Total distance traveled by the sound wave to the wall and back = Speed * Time = 330 * 2 = 660 meters. Distance to the wall = 660 / 2 = 330 meters.

This question belongs to: Maths Time Speed and Distance
Question #2
A person walks from his villa to a local station at 4 km/h and arrives 10 minutes late. If he routes at 5 km/h, he arrives 2 minutes early. Find the distance.
A. 3.5 km
B. 4.5 km
C. 5.0 km
D. 4.0 km

Correct Answer: Option D


Explanation:
Time difference = 10 - (-2) = 12 minutes = 12/60 = 0.2 hours. Let distance be d. d/4 - d/5 = 0.2 => d/20 = 0.2 => d = 4 km.

This question belongs to: Maths Time Speed and Distance
Question #3
A shoplifter sprints from a mall sector at 6:00 PM at 12 km/h. The security detail discovers the lapse and pursues at 6:30 PM at 16 km/h. At what time will the detail intercept the shoplifter?
A. 8:30 PM
B. 9:00 PM
C. 7:30 PM
D. 8:00 PM

Correct Answer: Option D


Explanation:
In 30 minutes (from 6:00 to 6:30 PM), the shoplifter covers 12 * 0.5 = 6 km. Relative speed of pursuit = 16 - 12 = 4 km/h. Time to catch = 6 / 4 = 1.5 hours. Interception time = 6:30 PM + 1.5 hours = 8:00 PM.

This question belongs to: Maths Time Speed and Distance