A boat goes 24 km upstream and 28 km downstream in 6 hours. It goes 30 km upstream and 21 km downstream in 6 hours 30 minutes. Find the speed of the boat in still water. MCQ with Answer and Explanation
A boat goes 24 km upstream and 28 km downstream in 6 hours. It goes 30 km upstream and 21 km downstream in 6 hours 30 minutes. Find the speed of the boat in still water.
A. 10 km/h
B. 14 km/h
C. 8 km/h
D. 12 km/h
Answer: Option A
Solution (By JKSSB Mock Tests)
Let 1/u = x and 1/d = y. 24x + 28y = 6 and 30x + 21y = 6.5. Solving these linear equations gives x = 1/6 and y = 1/14. So upstream speed u = 6 km/h, downstream speed d = 14 km/h. Speed in still water = (d + u)/2 = (14 + 6)/2 = 10 km/h.
Two cars start from the same spot and travel along perpendicular roads. One travels at 30 km/h and the other at 40 km/h. Find the distance between them after 1 hour.
Explanation:
In 1 hour, the first car travels 30 km and the second car travels 40 km. Direct distance = sqrt(30^2 + 40^2) = sqrt(900 + 1600) = sqrt(2500) = 50 km.
No comments yet. Be the first to start the discussion!