CUET Preparation Today
CUET
General Test
Numerical Ability
Boats and Streams
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. |
4 km/hr, 13 km/hr 12 km/hr, 4 km/hr 17 km/hr, 9 km/hr None of the above |
4 km/hr, 13 km/hr |
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 |