Question

about Travels a distance of 80 km in 4 hours upstream and same distance downstream in 2 hours then the velocity of heat and stream in kilometre per hour are​

Answer 1

Answer:

Explanation:

If ratio of time = DS:US = 2:2.50 = 4:5

=> Speed ratio = 5:4

Let the DS & US speeds be 5a & 4a respectively.

=> ( 5a - 4a)/2 = 4 = speed of stream

=> a = 8

Speed of boat= (DS + US)/2

= (40 + 32)/2 = 36 Kmph.

:-)

Answer 2

Answer:

Explanation:

Let us consider the velocities of the boat and stream be x and y respectively

We know that

speed = distance/time

So considering upstream,

⇒ x - y = 80/4

⇒ x - y = 20 ___________(1)

Now considering downstream,

⇒ x + y = 80/2

⇒ x + y = 40 ___________(2)

Adding (1) and (2) we have

x - y + x + y = 20 + 40

⇒ 2x = 60

⇒ x = 30

Thus the speed of the boat is 30km/h.

Putting the value of x in (2) we have

30 + y = 40

⇒ y = 40 - 30

⇒ y = 10

Thus speed of stream is 10km/h.

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