Answer: Option D Explanation:Let the speed of the boat in still water be x km/hr. then,
speed downstream = (x+3) km/hr, speed upstream = (x-3) km/hr.
Therefore (x+3)*1 = (x-3)*3/2 <=> 2x+6 = 3x-9 <=> x=15km/hr.
Answer: Option C Explanation:Let speed upstream be x km/hr.then, speed downstream = 3x km/hr.
speed in still water = 1/2 (3x+x) km/hr = 2x km/hr.
Therefore 2x =28/3 => x= 14/3.
so, speed upstream = 14/3 km/hr ; speed downstream =14 km/hr
Hence, speed of the current = 1/2 (14- 14/3) km/hr = 14/3 km/hr =4 2/3 km/hr.
Answer: Option B Explanation:Speed downstream = (14+4) km/hr = 18 km/hr;
Speed upstream = (14-4) km/hr = 10 km/hr.
Let the distance between A and B be x km. then,
x/18+(x-2)/10=19 <=> x/18+x/20 =19 <=> 19x/180 =19 <=> x =180 km.
Answer: Option A Explanation:Speed downstream = (5+1) km/hr = 6 km/hr ; speed upstream = (5-1) km/hr = 4 km/hr.
Let the required distance be x km.
Then, x/6 + x/4 = 1 <=> 2x+3x =12 <=> 5x =12 <=> x = 2.4 km.
Answer: Option D Explanation:Speed downstream =(15+3) km/hr = 18 km/hr.
distance traveled = (18*12/60) km = 3.6 km.