Answer:
Let the speed of the boat in still water be x km/h and
that of the stream be Then,
Speed upstream
Speed downstream
Now, time taken to cover 32 km upstream Time
taken to cover 36 km downstreamThe
total time of journey is 7 h.
?(i)(1/2)
Time taken to cover 40 km upstream Time
taken to cover 48 km downstream In this
case, total time of journey is 9 h.
?(ii)
Putting and in Eqs.
(i) and (ii), we get
?(iii)
and
?(iv)(1/2)
By cross-multiplication, in Eqs
(iii) and (iv) we have
(1/2)
and (1/2)
We have,
?(v)
and
?(vi)(1)
On adding Eqs. (v) and (vi), we
get
On putting the value of in Eq.
(vi), we get
Hence, the speed of the boat =
10 km/h and the speed of the stream = 2 km/h (1/2)
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