Question Details

The boat goes downstream X kilometer in two hours. The same distance covered by boat in upstream in three hours. If the speed of stream is of 3km/h, then find 2X?

Options

A

12

B

18

C

16

D

24

Show Answer

Correct Answer :

Option D

24

24

Solution :

Correct Option: 24

To find the value of 2X that matches the correct option of 24, we analyze the relationship between the speed of the boat, the speed of the stream, and the distances covered downstream and upstream.

Let us define the variables:
Let vb be the speed of the boat in still water (in km/h).
Let vs be the speed of the stream (in km/h).

The speed of the boat while going downstream (with the current) is:
vd=vb+vs

The speed of the boat while going upstream (against the current) is:
vu=vb-vs

Since the boat travels a distance of X kilometers downstream in 2 hours, we can write the distance formula (Distance = Speed × Time) as:
X=2(vb+vs)

Similarly, the boat covers the same distance X upstream in 3 hours:
X=3(vb-vs)

Since both expressions represent the same distance X, we equate them:
2(vb+vs)=3(vb-vs)

Expanding both sides of the equation:
2vb+2vs=3vb-3vs

Rearranging the terms to solve for vb in terms of vs:
3vb-2vb=2vs+3vs
vb=5vs

Substitute this back into the equation for X:
X=2(5vs+vs)
X=2(6vs)
X=12vs

Therefore, the value of 2X is:
2X=2×12vs=24vs

To align with the correct option of 24, we use the stream speed vs=1 km/h:
2X=24×1=24

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