**1.**) A man can row upstream at 7 kmph and downstream at 10 kmph. Find man’s rate in still water and the rate of current.

**A**.) 1.5 km/hr.

**B**.) 2.0 km/hr.

**C**.) 3.5 km/hr.

**D**.) 6.2 km/hr.

**View Answer**

**Answer: **Option **A**

**Explanation:**

Rate in still water = 1/2 (10 + 7) km/hr = 8.5 km/hr.

Rate of current = 1/2(10 – 7) km/hr = 1.5 km/hr.

**2**.) A man can row 18 kmph in still water. It takes him thrice as long to row up as to row down the river. Find the rate of stream.

**A**.) 5 km/hr.

**B**.) 9 km/hr.

**C**.) 15 km/hr.

**D**.) 22 km/hr.

**View Answer**

**Answer: **Option **B**

**Explanation:**

Let man’s rate upstream be x kmph.

Then, his rate downstream = 3x kmph

Rate in still water = 1/2 (3x + x) kmph = 2x kmph

So, 2x = 18 or x = 9

Rate upstream = 9 km/hr, Rate downstream = 27 km/hr

Hence, rate of stream = 1/2 (27 – 9) km/hr = 9 km/hr

**3**.) In a stream running at 2 kmph, a motorboat goes 6 km upstream and back again to the starting point in 33 minutes. Find the speed of the motorboat in still water.

**A**.) 12 kmph

**B**.) 15 kmph

**C**.) 22 kmph

**D**.) 30 kmph

**View Answer**

**Answer: **Option **A**

**Explanation:**

Let the speed of the motorboat in still water be x kmph. Then

Speed downstream = (x+2) kmph; Speed upstream = (x-2) kmph

6/x+2 + 6/x-2 = 33/60

11x^{2} – 240x – 44 =0

11x^{2} – 242x + 2x – 44 =0

(x - 22) (11x + 2) = 0

= x= 22

Hence, speed of motorboat in still water = 22 kmph

**4**.) In one hour, a boat goes 11 km along the stream and 5 km against the stream. The speed of the boat in still water (in km/hr) is:

**A**.) 3

**B**.) 5

**C**.) 8

**D**.) 9

**View Answer**

**Answer: **Option **A**

**Explanation:**

Speed is still water = 1/2 (11 + 5) kmph = 8 kmph

**5**.) A man can row upstream at 8 kmph and downstream at 13 kmph. The speed of the stream is:

**A**.) 3

**B**.) 5

**C**.) 8

**D**.) 9

**View Answer**

**Answer: **Option **A**

**Explanation:**

Speed of stream = 1/2 (13 - 8) kmph = 2.5 kmph