Boats and Streams - Concepts and Tricks Video Lecture | IBPS PO Prelims & Mains Preparation - Bank Exams

hi friends I am current from Demers in
this video I will show you how to solve
bought and seen problems so let's begin
first of all let us understand what do
you mean where downstream and upstream
if the boat is moving in the direction
of the stream then we call it as down 3
but if the boat is moving in the
opposite direction of the stream so we
call it as upstream in the downstream
the speed of the boat increases because
the river is also flowing in the same
direction and both the speeds add up but
in the upstream the speed of the wood
decreases because the direction of the
river is indifferent so let's see the
first inside let us say the speed of the
boat in the still water is you km/h so
then we have the speed of the stream
equals to V kilo meter per hour then the
speed of the boat in downstream will be
equals to u plus V kilometers per hour
and the speed of boat in upstream will
be equals to u minus V kilometers per
hour
so let us go to the inside to
like the speed of the boat in downstream
equals to a and the speed of the boat in
upstream equals to B km/h so now the
speed of the boat in the still water
will be equals to a plus B divided by 2
kilometres per hour and the speed of
stream will be equals to a minus B
divided by 2 kilometers per hour you
have to remember this thing we'll use
this in the next following problems
let's take a problem
a man can row upstream at 7 kilometers
per hour and downstream at 10 kilometers
per hour so find the man's rate in
Stillwater and rate of the current first
of all we have the speed of the
downstreams
equals 210 kilometers per hour and the
speed of upstream equals 270 liters per
hour so according to the formula the
speed of the boat in still water is
equal to a plus B divided by 2 which
gives us 10 plus 7 divided by 2 equals 2
8.5 km/h next we have the speed of
current which is a minus B divided by 2
equals 2
10 minus 7 divided by 2 which gives us
1.5 kilometers per hour let's see the
problem to a board can travel with the
speed of 13 kilometers per hour in still
water
if the speed of the stream is 4
kilometers per hour find the time taken
by the boat to go 68 kilometers fene so
first of all we have the speed of the
downstream which is equals to the speed
of boat in still water Plus speed of the
stream which is equal to 13 plus 4
equals to 17 kilometers per hour
next we have the distance equals to 68
kilometers and the speed equals to 17
kilometers per hour so we have to find
the time we'll use a formula distance
equals to speed into time so now we have
time equals to distance upon speed which
is 68 by 70 equals to 4 kilometers per
hour this is the answer
let's see another problem a motorboat
who speed is 15 kilometers in still
water goes 30 kilometers downstream and
comes back in a total of 4 hours and 30
minutes the speed of the stream in
kilometer per hour is so we have to find
the speed of the stream in kilometers
per hour so we got let's say the speed
of the stream equals 2x kilometers so
now we have the speed of downstream
equals to 15 plus X and the speed of
upstream will be close to 15 minus X
pretty simple right so next we have the
total time given which is equals to 4.5
hours which is the sum of the time taken
to go downstream and the time taken to
go upstream but remember in both the
cases this sense is 30 kilometers so we
have a total global distance of 60
kilometers so we use distance upon time
gives us the distance from speed gives
us time so we guide 30 point 15 plus X
is the time taken to go downstream and
30 point 15 minus X gives us the time
taken to go upstream so when we add both
of them it's a total time equals to 4.5
so when you solve this equation we get x
equals to 5 kilometers per hour which is
our answer so now guys lot of more
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rockin good bye
you