Aptitude - Boats and Streams - Discussion

Let the distance be X in km.

And speed formula is given by;
speed(or velocity)=distance/time taken.
Speed Upstream= (5-1)=4 kmph.
Speed downstream =(5+1)=6 kmph.
( given time taken to come back is 1hr.)

*Equating time take during Upstream and downstream to 1hour. ie
Time(up strm) +Time(dwn strm) =1---> Eq(1)
(time=distance *speed) so Eq(1)becomes.
X/6 + X/4 =1.
Taking lcm of 6&4 we get 12.
3x+2x=12.
5x=12.
So x=2.4km.

I think you guys got it. Correct me if I have done wrong.

Average Speed during toatal journey=2(6)(4)/(6+4)
=4.8 kmph
so, Total distance coverd during the Journey=Time* Average speed
=1*4.8
=4.8km
so, How far is the place = 4.8/2
= 2.4 km

Because man goes and come back.

Hi friends, in the above explanations we have taken;

time = Distance/Speed
If we take,
distance = speed * time, then;
d=[(u+v)+(u-v)]t.

So, it becomes 10km. This will be the total distance covered by man(including coming back.)
if we want only the distance to a place then it will be 5km.

Why should we not consider this format? can anyone tell me?

Speed downstream = (5 + 1) kmph = 6 kmph.
Speed upstream = (5 - 1) kmph = 4 kmph.

T = 1hr.
total time = (downstream speed/speed of downstream)+(distance of upstream/speed of Upstream).

we don't know distance so let it be 'x'
so, 1 = x/6 + x/4.
take lcm and do eqaution u will get
2x + 3x = 12,
5x = 12,
x = 2.4 km.

Why do we need to calculate the downstream and upstream when we already the have speeds of boat(u) and speed of stream(v)? We can directly calculate the time from that.

Like-
u=5
v=1
t=1

Let the distance be x.
So x/5+x/1=1.
Solving the equation we will get the value of x which is 5/6.(but incorrect value).

I solve this question and I got a different answer i.e. 10 km is the distance.

Upstream speed = 5km/h - 1km/h = 4.
Downstream speed = 5km/h + 1km/h = 6.

Distance =( upstream Speed * time) + (downstream speed * time).
= 4 * 1 + 6 * 1.
=. 10.

For Who don't understand how come 12, please refer the following.

x/6 + x/4 = 1
then cross multiply we get;
4x+6x/24 = 1,
24 move to another side we get ;
4x+6x = 24,
divided by 2 for simplify we get;
2x+3x = 12.

Boat => 5.
Water => 1
Downstream = 5+1 = 6.
Upstream = 5-1 = 4.

D = T*S
D = 1 * (6)(4)/10.
Then D. = 2.4.

Here Speed = Product of two speeds/ Sum of two speeds.

Easy way to solve this type of question is followed by a simple formula.
i.e
D = T[sb square - ss square]/2*sb.

sb means the speed of a boat.
ss means the speed of a stream.

I think answer to how far is the place should be 1.2 km. And answer to how much distance man has covered should be 2.4 km. He goes and comes back. Suggestions please.