- 1. Find the speed of stream if a boat covers 36 km in downstream in 6 hours which is 3 hours less in covering the same distance in upstream?

Options- A. 1.5 kmph
- B. 1 kmph
- C. 0.75 kmph
- D. 0.5 kmph

Correct Answer: 1 kmph

Speed of the boat upstream = 36/9 = 4 kmph

Speed of the boat in downstream = 36/6 = 6 kmph

Speed of stream = 6-4/2 = 1 kmph

- 2. A man can row against the current three fourth of a kilometer in 15 min and returns same distance in 10 min, then ratio of his speed to that of current?

Options- A. 5:1
- B. 3:1
- C. 4:1
- D. 2:1

Correct Answer: 5:1

Let the speed of the man in still water = **p** kmph

Speed of the current = **s** kmph

Now, according to the questions

**(p + s) x 10 = (p - s) x 15**

2p + 2s = 3p - 3s

**=> p : s = 5 : 1**

Hence, ratio of his speed to that of current** = 5:1.**

- 3. Sravan drove from home to a neighboring town at the speed of 50 km/h and on his returning journey, he drove at the speed of 45 km/h and also took an hour longer to reach home. What distance did he cover?

Options- A. 350 kms
- B. 450 kms
- C. 900 kms
- D. 700 kms

Correct Answer: 900 kms

Let the distance he covered each way = d kms

According to the question,

**d/45 - d/50 = 1**

**=> d = 450 kms.**

Hence, the total distance he covered in his way =** d + d = 2 d = 2 x 450 = 900 kms.**

- 4. A motorboat takes half time to cover a certain distance downstream than upstream. What is the ratio between rate of current and rate of boat in still water?

Options- A. 1 : 3
- B. 3 : 2
- C. 2 : 3
- D. 3 : 1

Correct Answer: 1 : 3

Let the speed of the boat in still water is 'w'

Speed of the current is 'c'

Let the distance between two places is 'd'

According to the question, motorboat takes half time to cover a certain distance downstream than upstream.

$\frac{\mathbf{d}}{\mathbf{w}\mathbf{+}\mathbf{c}}\mathbf{}\mathbf{=}\mathbf{}\frac{\mathbf{1}}{\mathbf{2}}\left(\frac{{\displaystyle \mathbf{d}}}{{\displaystyle \mathbf{w}\mathbf{-}\mathbf{c}}}\right)$

=> 2w - 2c = w + c

=> w = 3c

=> c : w = 1 : 3

Hence, the ratio between rate of current(c) and rate of boat in still water(w) = **1 : 3**

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