Question
Download Solution PDFA motor boat travelled to a point B from A and returned to A. The speed of the stream is 3 km/hr. If distance between A and B is 2 km and total time taken for the round trip is 30 minutes, then speed of the motor boat in still water is:
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFGiven:
Distance from A to B = 2 km
Total distance (round trip) = 4 km
Speed of stream = 3 km/hr
Total time taken = 30 min = 0.5 hr
Let speed of motor boat in still water = x km/hr
Formula used:
Downstream speed = x + 3
Upstream speed = x - 3
Time = Distance ÷ Speed
Total time = Time down + Time up
Calculation:
⇒ 2(x - 3) + 2(x + 3) = 0.5(x2 - 9)
⇒ 2x - 6 + 2x + 6 = 0.5(x2 - 9)
⇒ 4x = 0.5x2 - 4.5
⇒ x2 - 8x - 9 = 0
Solve the quadratic:
⇒ (x - 9) (x + 1) = 0
⇒ x = 9 or x = -1
∴ Speed of motor boat in still water is 9 km/hr
Last updated on Sep 27, 2023
The Telangana Police SI Notification is expected to be released soon. The TSLPRB has concluded the previous cycle recently on in August 2023. The upcoming notification is a golden opportunity for candidates who want to join the police force in the state of Telangana. Candidates must attempt the Telangana Police SI mock tests. The Telangana Police SI previous year papers can be downloaded here.