MCQ Test: Boat and Stream- 2 - Bank Exams MCQ

To solve this question, we can apply a short trick approach;
A person can row a a speed of ‘x’  in still water. If stream is flowing at a speed of ‘y’, it takes time ‘T’ to row to a place and back, then distance 

between two placed is given by 
Given, 
Total Time (T) = 32 min = 32/60 = 8/15hr
By the short trick approach, we get


Hence, option C is correct.

To solve this question, we can apply a short trick approach;

By the short trick approach, we get


Hence, option C is correct.

To solve this question, we can apply a short trick approach
x = 1/2 (boat’s rate with current + his rate against current)
Given,
x is the boat’s rate in still water 
By the short trick approach, we get

Hence, option D is correct.

To solve this question, we can apply a short trick approach;
Speed of current
= 1/2 (Rate of downstream – Rate of upstream)
By the short trick approach, we get
= 1/2 (16 – 11) = 5/2 = 2.5 kmph.
Hence, option D is correct.

Given,
Speed of boat in downstream = 15 km/hr
Speed of current = 3 km/hr
Speed of boat in still water = 12 km/h
Time taken at upstream

= 1 hour 40 minutes
Time taken at downstream

∴ Total time = 2 hours 40 minutes

Given, Speed downstream = 8 km/h Speed upstream = 6 km/h 
∴   Speed of boat in still water



Hence, option C is correct.

Let the required distance be x km, then As per the question, Time_downstream + Time_upstream  =  Total time



⇒  5x = 60 x 15  ⇒  x = 180 km
Hence, option A is correct.

Let the speed of the stream be x kmph and both the boats meet after t hours.
 According to the question,
Distance covered while going downstream + Distance covered while going upstream = Total Distance 
⇒  (16 + x) t + (14 – x) t = 150
⇒  16t + 14t = 150
⇒  30t = 150
⇒  t = 5 hrs
Hence, option C is correct.

Let the speed of stream be x kmph
∴   Rate upstream = 15/2 - x
And rate downstream = 15/2 + x
Let's also assume the time taken in downstream and upstream is 1 hr and 4 hrs respectively. We know that, Distance = Speed × Time

⇒  (15 + 2x) = (60 – 8x) ⇒  10x = 45

Hence, the option D is correct.

Let the required distance be x km. As per the question, Time_upstream – Time_downstream = 3




⇒  x = 3 × 8 = 24 km.
Hence, option B is correct.

Let the speed of the stream be x km/hr
Then speed downstream = (10 + x) km/hr
Speed upstream
= (10 − x) km/hr

⇒ 260 − 26x = 140 + 14x
⇒ 40x = 120
⇒ x = 3 km/hr

Let the speed of current be = c km/hr

Let the speeds of A and B in still water be 3k km/hr and 2k  km/hr

Upstream speed of A = (3k – c) km/hr

Downstream speed of B = (2k + c) km/hr

Distance between A and B after 3 hrs = [3 (3k – c) + 3 (2k + c)] km

= (9k – 3c + 6k + 3c) km 

= 15k km

After stream becomes stationary

Relative speed when both go in same direction = (3k – 2k) km/hr = k km/hr

Time after which they meet = 15 k/ k = 15 hrs

Hence, option B is correct.

S + W = 14 . . . . . . (i)
S - W = 8 . . . . . . . .(ii)
_________________
from equation (i) & (ii)
S = 11 km/hr, W = 3 km/hr
Speed of current = 3 km/hr

Man's rate in still water
= (15 - 2.5) km/hr
= 12.5 km/hr.
Man's rate against the current
= (12.5 - 2.5) km/hr
= 10 km/hr.

Let the speed of the stream be x km/hr
Then,
Speed downstream = (15 + x) km/hr
Speed upstream = (15 - x) km/hr

Rate downstream
= 16/2 kmph = 8 kmph
Rate upstream
= 16/4 kmph = 4 kmph
∴ Speed in still water
= 1/2(8 + 4) kmph = 6 kmph

Let the speed of the stream x mph.
Then,
Speed downstream = (10 + x) mph
Speed upstream = (10 - x) mph

Let man's rate upstream be x kmph
Then, his rate downstream = 2x kmph
∴ (speed in still water) : (Speed of stream)

Time taken to cover 50 miles downstream

Time taken to cover 50 miles upstream

Total time taken to cover 100 miles

Relative speed = 20 + 5 = 25 km/hr
Time = 100/25 = 4 hours