Required time = (4 / 15) x 63 hrs.
= 16 hrs. 48 min
Distance = (4 x 11/4 )km.
= 11 km.
? Req. Time = 11km / (33/2) km/hr
= 2 x (11 / 33) hr.
=(2 / 3) x 60 minutes
= 40 minutes
Let The required distance be y km.
Then, y/3 + y/2 = 5
? 2y + 3y = 30
? y = 6 km
Let total distance be y km.
Then , (2y / 3) / 4 + ( y / 3) / 5 = 42/60
? y/6 + y/ 15 = 7/10
? 5y + 2y = 21
? y = 3
? Required distance = 3 km.
Let the total journey be x km. then,
2x/15 + 9x/20 + 10 = x
? 8x + 27x + 600 = 60x
? x = 24
? Total journey = 24 km.
Let the total distance be y km.
Then, (y/2) x (1/60) + (y/2) x (1/50) = 44/3
? y/120 + y/100 = 44/3
? 5y + 6y = 8800
? y = 800
? Required distance = 800km.
Speed in m/sec = ( 5 / 18 ) x Speed in kms/hr.
92.4 kms/hr = 92.4 x (5 / 18) m/sec.
? Req. distance = 92.4 x ( 5 / 18 ) x 600 meters
= 15400 m.
Speed = 10.2 / 3 km/hr.
= 3.4 km/hr.
Distance covered in 5 hours = 3.4 X 5 km.
= 17 km
Speed = 600 / (5 x 60) m/sec.
= 600 / (5 x 60) x 18/5 km/hr.
= 7.2 km/hr.
Average Speed = Total distance / time
= 2d / [( d / 16) + ( d / 9)]
= ( 2 x 16 x 9 ) / ( 16 + 9 ).
= 11.52 km/hr.
Shortcut :
Average speed = 2uv / (u + v)
= ( 2 x 16 x 9 ) / ( 16 + 9 )
= 11.52
Speed in km/hr = speed in m/sec x (18 / 5 )
Speed in km/hr = (22.5 x 18 /5 ) km/hr
= 81 km/hr.
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