Question

A boat takes 8 hours to travel 30 km upstream and 36 km downstream ; but it takes 10 hours travel 36 km upstream and 48 km downstream find the speed of the boat in still water and find the speed of stream

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Answer 1

Answer:

Step-by-step explanation:

Total Time =

Upstream distance/upstream speed + Downstream dist/downstream speed  

Let speed of boat=x

Let speed of stream=y

Upstream speed = speed of boat - speed of stream = x - y 

Down stream speed = speed of boat + speed of stream = x + y

Given 36/x+y + 24/x-y = 6 hours...... (i)

48/x+y + 40/x-y = 9 hours.......(ii)

Multiply eq.(i) by '5' and eq.(ii) by '3'

180/x+y + 120/x-y = 30.....(iii)

144/x+y + 120/x-y = 27.....(iv)

Subtract above equations:

36/x+y = 3

x+y = 12.....(a)

(a) in (iv)

144/12 + 120/x-y = 27

12 + 120/x-y = 27

120/x-y = 15

x-y = 8

x+y = 12

Adding both:

2x = 20

x=10

10+y = 12

y=2

Speed of boat in still water = 10 kmph

Speed of stream = 2 kmph

Hope this helps

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