A person row a boat 12 km downstream in 1 hour. If the river current flows at 3 km/h, find the time taken by the boat to row the same distance upstream. MCQ with Answer and Explanation
Question
Report Error
Discuss this Question (0)
Practice More Time Speed and Distance Questions
Question #1
Report Error
A person has to cover a distance of 160 km. He covers the first half of the distance at 40 km/h. At what speed must he travel the remaining half to make the average speed for the whole journey 50 km/h?
Correct Answer: Option C
Explanation:
Let the required speed for the second half be x km/h. Using the average speed formula for equal halves: Average Speed = 2v1*v2 / (v1 + v2) => 50 = (2 * 40 * x) / (40 + x) => 50(40 + x) = 80x => 2000 + 50x = 80x => 30x = 2000 => x = 66.67 km/h.
Let the required speed for the second half be x km/h. Using the average speed formula for equal halves: Average Speed = 2v1*v2 / (v1 + v2) => 50 = (2 * 40 * x) / (40 + x) => 50(40 + x) = 80x => 2000 + 50x = 80x => 30x = 2000 => x = 66.67 km/h.
This question belongs to:
Maths
Time Speed and Distance
Question #2
Report Error
A person can row 8 km/h in still water. He finds that it takes him thrice as long to row upstream as to row downstream. Find the speed of the current.
Correct Answer: Option C
Explanation:
Let current speed be c. Upstream speed = 8 - c, Downstream speed = 8 + c. Given: 3 * (8 - c) = 8 + c => 24 - 3c = 8 + c => 4c = 16 => c = 4 km/h.
Let current speed be c. Upstream speed = 8 - c, Downstream speed = 8 + c. Given: 3 * (8 - c) = 8 + c => 24 - 3c = 8 + c => 4c = 16 => c = 4 km/h.
This question belongs to:
Maths
Time Speed and Distance
Question #3
Report Error
A sedan covers a distance path of 480 km at a uniform tracking speed. If the speed index is lowered by 10 km/h, the trip records 2 hours longer. Find the original baseline speed.
Correct Answer: Option B
Explanation:
Let original speed be s. 480 / (s - 10) - 480 / s = 2 => 240 / (s - 10) - 240 / s = 1 => 2400 = s(s - 10). Solving s^2 - 10s - 2400 = 0 gives (s - 50)(s + 40) = 0. Baseline speed = 50 km/h.
Let original speed be s. 480 / (s - 10) - 480 / s = 2 => 240 / (s - 10) - 240 / s = 1 => 2400 = s(s - 10). Solving s^2 - 10s - 2400 = 0 gives (s - 50)(s + 40) = 0. Baseline speed = 50 km/h.
This question belongs to:
Maths
Time Speed and Distance
No comments yet. Be the first to start the discussion!