Aptitude Shortcuts Method for Boats & Streams Related Problems | Download in PDF

Aptitude Shortcuts Method for Boats & Streams Related Problems
Aptitude Shortcuts Method for Boats and Streams Problems | Download in PDF:
Aptitude Shortcuts methods that used in aptitude questions related to Boats and Streams Problems were given below in pdf. Candidates those who are preparing for SSC/FCI and all other competitive exams can use this.



QUESTION
A boat travels upstream from B to A and downstream from A to B in 3 hours. If the speed of the boat in still water is 9km/hr and the speed of the current is 3km/hr, find the distance between A and B?

GIVEN:
Speed of boat in still water, a = 9km/hr
Speed of stream, b = 3km/hr
Time taken to travel from A to B and B to A, T = 3 hours

SOLUTION:

NORMAL METHOD:

Speed Downstream = (a + b) km/hr
                                 = (9+3) = 12 km/hr
Speed Upstream = (a – b) km/hr
                            = (9 – 3) = 6 km/hr
Let the distance travelled, D = X km
Then, [X/speed downstream] + [X/speed upstream] = Time taken to travel
[X/12] + [X/6] = 3
[X + 2X] / 12 = 3
X + 2X = 36
3X = 36
X = 36/3 = 12
Therefore Distance travelled, D = X = 12km

ALTERNATE METHOD:

Distance = [Time × (a– b2)] / 2a
Where, a = speed of boat in still water
             b = speed of stream
D = [3 × (92 – 32)] / (2 × 9)
D = [3 × (81 – 9)] / 18
D = [3 × 72] /18 = 3×4