A boat travels 68 km. downstream and 45 km. upstream in 9 hrs. If boat travels 51 km. downstream and 72 km. upstream in 2 hrs more, then find speed of stream and speed of boat in still water.
Answer & explanation
Correct answer: option 1
Let the speed of boat = U km/hr.
Speed of stream = V km/hr.
ATQ, \(\frac{68}{U+V}\) + \(\frac{45}{U - V}\) = 9 -----------(i)
\(\frac{51}{U+V}\) + \(\frac{72}{U-V}\) = 11 ----------- (ii)
Note : - Take help of common factor for speedy calculations
(68, 55) and (45, 72)
⇓ ⇓ ⇓ ⇓
17 9
So, U+V = 17 and U-V = 9 satisfy the equation
Then, U = 13 km/hr and V = 4 km/hr