| Topic Included: | Formulas, Definitions & Exmaples. |
| Main Topic: | Quantitative Aptitude. |
| Quantitative Aptitude Sub-topic: | Time Speed and Distance Aptitude Notes & Questions. |
| Questions for practice: | 10 Questions & Answers with Solutions. |
We are discussing different cases of Boat and Stream here to understand the scenario easily.
Note: If speed of water flow is zero then the speed of boat (\(B_s\)) will be normal.
Case (1): If boat and water moving in the same direction (moving downstream) then speed of boat (\(B_s\)) will be- $$ B_s = D_s - S_s $$
Where,\(B_s\) = Speed of boat.\(D_s\) = Speed of downstream.\(S_s\) = Speed of stream.
Example (1): If a boat goes downstream at the speed of \(10 \ km/hr\), and the speed of stream is \(5 \ km/hr\), then find out the speed of the boat in still water?
Solution: Given values,Speed of downstream \((D_s) = 10 \ km/hr\),Speed of stream \((S_s) = 5 \ km/hr\), then speed of boat in still water, $$ (B_s) = D_s - S_s $$ $$ (B_s) = 10 - 5 = 5 \ km/hr $$
Example (2): If a man swim \(60 \ km\) downstream taking \(2 \ hours\), and the speed of stream is \(10 \ km/hr\) then find out the speed of the man in still water?
Solution: Given values,Speed of downstream \((D_s) = \frac{60}{2} = 30 \ km/hr\),Speed of stream \((S_s) = 10 \ km/hr\), then speed of man in still water, $$ (B_s) = D_s - S_s $$ $$ (B_s) = 30 - 10 = 20 \ km/hr $$
Case (2): If boat and water moving in the opposite direction (moving upstream) then speed of boat (\(B_s\)) will be- $$ B_s = U_s + S_s $$
Where,\(B_s\) = Speed of boat.\(U_s\) = Speed of upstream.\(S_s\) = Speed of stream.
Example (1): If a boat goes upstream at the speed of \(20 \ km/hr\), and the speed of stream is \(10 \ km/hr\), then find out the speed of the boat in still water?
Solution: Given values,Speed of upstream \((U_s) = 20 \ km/hr\),Speed of stream \((S_s) = 10 \ km/hr\), then speed of boat in still water, $$ (B_s) = U_s + S_s $$ $$ (B_s) = 20 + 10 = 30 \ km/hr $$
Example (2): If a boat goes \(100 \ km\) upstream taking \(4 \ hours\) and the speed of stream is \(7 \ km/hr\), then find out the speed of the boat in still water?
Solution: Given values,Speed of upstream \((U_s) = \frac{100}{4} = 25 \ km/hr\),Speed of stream \((S_s) = 7 \ km/hr\), then speed of boat in still water, $$ (B_s) = U_s + S_s $$ $$ (B_s) = 25 + 7 = 32 \ km/hr $$