Q. 2 A3.9( 22 Votes )

# <span lang="EN-US

Let the speed of the boat in still water be x km/h and speed of the stream be y km/h

Speed of boat upstream = (x – y) km/h

Speed of boat downstream = (x + y) km/h

But, total time of journey is 10hrs. = 10 = 13

Let be a and be b

30a + 44b = 10 …I

40a + 55b = 13 …II

Multiply Eq. I by 4 and Eq. II by 3

120a + 176b = 40

120a + 165b = 39

_- - - _

11b = 1

b = substituting value of b in Eq. I

30a + 44× = 10

30a + 4 = 10

30a = 6

a =   5 = x + y 5 = x + y   11 = x - y 11 = x - y ….IV

x + y = 5

x – y = 11

2x = 16

x = 8

substitute value of x in Eq. III

8 + y = 5

Y = 3

Hence, Speed of boat = 8 km/h;

Speed of stream = 3 km/h

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