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1. If a boat goes 7km upstream in 42 minutes and the speed of the stream is 3kmph,then the speed of the boat in still water is-
- A. 4.2 km/hr
- B. 4.2 km/hr
- C. 4.2 km/hr
- D. 4.2 km/hr
Answer: Option C
Explanation:
Let, the speed of the boat in still water is x km/hr
the speed of stream in 3 km/hr
So, Upstrem speed of boat is ( x - 3) km/hr
According to question,
Upstrem speed of boat is = 7/42 km/mint
= (7×60)/42 km/hours = 10km/hours
So, x - 3 = 10
x = 10 + 3 = 13 km/hr
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