Question

D) A boat requires two hours to travel a distance of 30 km along the stream. It requires 1 hr. 20 min more. to travel the same distance in return journey. Find the speed of the stream and that of the boat in still water.​

Answer 1

Answer:

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Answer 2

Step-by-step explanation:

let speed of boat =S1

speed of stream=S2

total distance=30 km

1)time taken by boat to cover 30 km diastance when it moves along stream=2 hrs

2)time taken by boat to 30 km distance when it moves against ( return journey) = 2hrs+1hr 20 mins

= 3 hr 20 mins

=3+1/3 hrs

we know that. time=distance/speed

1) 2=30/(S1+S2)

S1+S2=15

2)3+1/3=30/(S1-S2)

10/3=30/(S1-S2)

S1-S2=9

by solving above two equations we get S1=12 km/ hr and S2=3 km/hr

speed of boat S1=12 km/ hr

speed of stream S2= 3 km/hr