Correct Answers: | |

Wrong Answers: | |

Unattempted: |

### Question 1

The difference of the squares of the downstream and upstream speeds of a boat in a stream is 28. What is the product of the speed of the stream and that of the boat in still water?

**A**

7.

**B**

8.

**C**

6.

**D**

10.

**Soln.**

**Ans: a**

Let the speed of the boat in still water be u, and let v be the speed of the stream. The difference of squares of the speeds is $(u + v)^2 - (u - v)^2$, which is $u^2 + v^2 + 2uv - (u^2 + v^2 - 2uv)$ = 4uv = 28. We get uv = $28/4$ = 7.

### Question 2

The speed of a boat in still water is 56 km/h. It takes the same time to travel an upstream distance of 11 km as it takes to travel a downstream distance of 17 km. The rate of flow of the stream is?

### Question 3

The difference of the squares of the downstream and upstream speeds of a boat in a stream is 12. What is the product of the speed of the stream and that of the boat in still water?

**A**

3.

**B**

4.

**C**

2.

**D**

6.

**Soln.**

**Ans: a**

Let the speed of the boat in still water be u, and let v be the speed of the stream. The difference of squares of the speeds is $(u + v)^2 - (u - v)^2$, which is $u^2 + v^2 + 2uv - (u^2 + v^2 - 2uv)$ = 4uv = 12. We get uv = $12/4$ = 3.

### Question 4

A man can row a boat at the rate of 14 km/h in still water, and at the rate of 4 km/h against the stream. At what rate can he row down the stream?

### Question 5

The speed of an aircraft in still air is 14 km/h and rate of wind is 8 km/h. If it travels along the direction of the wind for 7 hours, what is the distance travelled by the aircraft during the journey?

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This Blog Post/Article "Boats and Streams Quiz Set 009" by Parveen (Hoven) is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Updated on 2019-08-18.