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A boy rows downstream, covers some distance, and then comes back upstream in 8 hours. Calculate the distance covered if the speed of the boat in still water is 6 kmph and the speed of the stream is 4 kmph.1. 40 km2. 40/7 km3. 40/3 km4. 18 km |
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Answer» Correct Answer - Option 3 : 40/3 km Given: Speed of boat in still water = 6 kmph Speed of stream = 4 kmph U/S + D/S = 8 hours Formula used: Speed of boat in still water is a kmph and speed of stream is b kmph Speed D/S = (a + b) kmph Speed U/S = (a – b) kmph Calculations: Speed in still water = 6 kmph Speed of stream = 4 kmph ⇒ DS speed = 10 kmph ⇒ US speed = 2 kmph Assume distance to be D km ⇒ (D / 10) + (D / 2) = 8 ⇒ 6D/10 = 8 ⇒ D = 40/3 kms ∴ Distance covered is 40/3 kms |
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