A boat whose speed is 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream is ___ km/hr. Type your answer below!
Answers
Answer:Let speed of stream is x km/hr
the total distance is 30 kms.
Speed of boat in still water is 15 km/hr.
So in downstream
speed of boat (15+x)
time taken
to travel 30 kms is 30/(15+x)hrs.
In upstream speed is (15-x)
so time taken
to travel 30 kms is 30/(15-x)
total time taken by boat
30/(15+x)+30/(15-x)=4+1/2
30(15-x)+30(15+x)=9(225-x^2) /2
450+450=(2025–9x^2)/2
1800=2025–9x^2
9x^2 =225
3x=15
x=5 km/hr
Step-by-step explanation:
Ans is 5 km
Step-by-step explanation:
Let speed of stream is x km/hr
the total distance is 30 kms.
Speed of boat in still water is 15 km/hr.
So in downstream
speed of boat (15+x)
time taken
to travel 30 kms is 30/(15+x)hrs.
In upstream speed is (15-x)
so time taken
to travel 30 kms is 30/(15-x)
total time taken by boat
30/(15+x)+30/(15-x)=4+1/2
30(15-x)+30(15+x)=9(225-x^2) /2
450+450=(2025–9x^2)/2
1800=2025–9x^2
9x^2 =225
3x=15
x=5 km/hr