# Boats and Streams- Aptitude Questions and Answers

 If a man rows at 5 km/hr in still water and 3.5 km/hr against the current,then his rate along the current is ? A) 8.5 km/hr B) 6.5 km/hr C) 6 km/hr D) 4.25 km/hr Correct Answer : 6.5 km/hr Explanation :If The speed of boat or boatman in calm water is u kmph and The speed of water or stream is v kmph, then:In water, the speed along with stream= (u + v) kmph Speed of current = 5 - 3.5 = 1.5 km/hr. So the speed of man along the current = 5 + 1.5 = 6.5 km/hr The speed of a boat downstream is 15 km/hr and the speed of the stream is 1.5 km/hr. The speed of the boat upstream is ? A) 13.5 km/hr B) 16.5 km/hr C) 12 km/hr D) 8.25 km/hr Correct Answer : 12 km/hr Explanation :If The speed of boat or boatman in calm water is u kmph and The speed of water or stream is v kmph, then: Speed downstream= (u + v) kmph , In water, the speed along with stream Speed upstream = (u - v) kmph ,In water, the speed against the stream 15= u + 1.5 ⇒ u = 13.5 Speed upstream, u - v = (13.5 - 1.5) km/hr = 12 km/hr A boat goes 14 km upstream in 56 minutes. The speed of stream is 2 km/hr. The speed of boat in still water is ? A) 6 km/hr B) 15 km/hr C) 14 km/hr D) 17 km/hr Correct Answer : 17 km/hr Explanation :Speed upstream Speed(S) = Distance(d)/Time(t) = 14/56 km/min = 14*60/56 km/hr= 15 km/hr If The speed of boat or boatman in still water is U kmph and The speed of water or stream is V kmph, then: Speed upstream = (U - V) kmph ,In water, the speed against the stream 15 = U - 2 So speed of boat in still water , U = 17 km/hr A man can row upstream 32 km in 4 hours. If the speed of current is 2 km/hr, find how much he can go downstream in 6 hours ? A) 70 km B) 72 km C) 64 km D) 81 km Correct Answer : 72 km Explanation :Upstream Speed(S) = Distance(d)/Time(t) = 32/4 km/hr= 8 km/hr If The speed of boat or boatman in still water is U kmph and The speed of water or stream is V kmph, then: Speed upstream = (U - V) kmph 8 = U - 2 Speed of man in still water,U = 8 + 2 = 10 km/hr Speed of man in downstream = (U + V) kmph = (10 + 2) = 12 km/hr Now, man cover the distance in 6 hours = 12 * 6 = 72 km A man can row upstream at 15 km/h and downstream at 21 km/h. The speed of water current of the river is ? A) 8 km/h B) 6 km/h C) 3 km/h D) 5 km/h Correct Answer : 3 km/h Explanation :If the speed downstream is x kmph and the speed upstream is y kmph, then: Rate of stream = 1/2 (x - y) kmph. = 1/2(21 - 15) km/h = 3 km/h A man rows downstream 60 km and upstream 36 km, taking 4 hours each time. The speed of the man is : A) 15 km/h B) 16 km/h C) 8 km/h D) 12 km/h Correct Answer : 12 km/h Explanation :If the speed downstream is x kmph and the speed upstream is y kmph, then: Speed in still water = 1/2 (x + y) kmph. x = 60/4 =15 km/h y = 36/4 = 9 km/h speed of the man = (15 + 9) / 2 = 12 km/h The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is? A) 1.2 km B) 1.8 km C) 2.4 km D) 3.6 km Correct Answer : 3.6 km Explanation :Speed Downstream = (15 + 3) km/hr = 18 km/hr. Distance travelled =(18 * 12 / 60 )hrs = 3.6 km The speed of a boat in downstream is 12 km / h and in upstream is 8 km / h. The time taken by boat to cover 24 km in still water? A) 2 hours B) 3 hours C) 2.4 hours D) 1.2 hours Correct Answer : 2 hours Explanation :If The speed of boat or boatman in still water is U kmph and The speed of water or stream is V kmph, then: Speed upstream = (U - V) = 8 km/hr Speed of man in downstream = (U + V) kmph = 12 km/hr After solving above equations 2*U = 20 km/hr speed of boat in still water is,U = 10 km/hr Required time = 24 / 10 = 2.4 hr Speed of a boat in still water is 10 kmph, and speed of the stream is 5 Kmph. In how many minutes would the boat cover a distance of 5 km downstream? A) 20 minute B) 30 minute C) 40 minute D) 25 minute Correct Answer : 20 minute Explanation :boat speed = 10 km/hr and stream speed = 5 km/hr Thus net speed of boat in downstream = 10 + 5 = 15 km/hr Time taken to travelled 5 km distance time = distance / speed = 5/ 15 = 1/3 hr = 60/3 minutes = 20 minutes