Question
Speed of a boat in still water is 15 km/h while the
speed of the stream is ____ km/h. Total time taken by the boat to go 150 km upstream and 225 km downstream is ____ hours. The values given in which of the following options will fill the blanks in the same order to make the above statement true: A. 10, 38.25 B. 5, 25 C. 8, 34.375 D. 7, 33.5Solution
According to the question: For A: Speed of boat = 15 km/h Speed of stream = 10 km/h Speed in upstream = 15 - 10 = 5 km/h Speed in downstream = 15 + 10 = 25 km/h Total time = 150/5 + 225/25 = 30 + 9 = 39 hours So, A can't be the answer. For B: Speed of boat = 15 km/h Speed of stream = 5 km/h Speed in upstream = 15 - 5 = 10 km/h Speed in downstream = 15 + 5 = 20 km/h Total time = 150/10 + 225/20 = 15 + 11.25 = 26.25 hours So, B can't be the answer. For C: Speed of boat = 15 km/h Speed of stream = 8 km/h Speed in upstream = 15 - 8 = 7 km/h Speed in downstream = 15 + 8 = 23 km/h Total time = 150/7 + 225/23 ≈ 21.43 + 9.78 ≈ 31.21 hours So, C can't be the answer. For D: Speed of boat = 15 km/h Speed of stream = 7 km/h Speed in upstream = 15 - 7 = 8 km/h Speed in downstream = 15 + 7 = 22 km/h Total time = 150/8 + 225/22 ≈ 18.75 + 10.23 ≈ 28.98 hours So, D can't be the answer
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