Vijay rows 1500m in 1350 seconds against the stream and returns in 15 minutes. His rowing speed in s

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07 Dec 2020 BOATS AND STREAMS

Vijay rows 1500m in 1350 seconds against the stream and returns in 15 minutes. His rowing speed in still water is?

OPtion

1) 5km/hr
2) 4km/hr
3) 7km/hr
4) 9km/hr
5) 6km/hr
6) 5.5km/hr
7) 6.5km/hr
8) 4.5km/hr
9) 7.5km/hr
10) None of the above

Solution

Rate upstream = (1500 / 1350) m/s = (150/135) m/s = = 10/9 m/s
Rate downstream = (1500 / 900)m/s = (15/9)m/s = 5/3 m/s
Rate in still water = ½ [ a+ b] = ½[10 / 9 + 5 /3] = ½[10 +15 / 9]
= ½[25/9] = 25/18 m/s = (25/18) * (18/5)km/hr
speed in still water = 5km/hr

Correct Option: 1 Best Solution (3)

Billal Hossain   3 years AGO

Rate upstream = (1500/1350) = 10/9 m/s
here, 15 minutes= 900 s
Rate downstream (1500/900) m/s = 5/3 m/s
Rowing speed in still water = (1/2)*[(10/9) + (5/3)] m/s.
= 25/18 m/s
= (25/18)*(18/5) km/hr
= 5 km/hr
So, My option is (1)

Like? Yes (2) | No   

SAYAN CHATTERJEE   3 years AGO

1500/(x+y)= 1350
1500/(x-y)= 900
x= 5kmph.
Option 1.

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Varun   3 years AGO

Against = 1.5km/(1350/3600)hr = 4kmph
Return = 1.5km/0.25hr = 6kmph
Still = (4+6)/2 = 5kmph

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