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, $$ (B_s) = U_s + S_s $$ $$ (B_s) = 25 + 7 = 32 \ km/hr $$

Lec 1: Introduction to Time, Speed and Distance
Exercise-1
Lec 2: Concept of Train and Platform Case (1)
Exercise-2
Lec 3: Concept of Train and Platform Case (2)
Exercise-3
Lec 4: Concept of Train and Platform Case (3)
Exercise-4
Lec 5: Concept of Train and Platform Case (4)
Exercise-5
Lec 6: Concept of Acceleration
Exercise-6
Lec 7: Concept of Boat and Stream Case (1) and Case (2)
Exercise-7
Lec 8: Concept of Boat and Stream Case (3)
Exercise-8
Exercise-9
Exercise-10