Mathematics
A boat takes 2 hours to go 40 km down the stream and it returns in 4 hours. Find the speed of the boat in still water and the speed of the stream.
Linear Equations
117 Likes
Answer
Let speed of boat in still water be x km/h and speed of stream be y km/h.
Speed of boat downstream = (x + y) km/h
Speed of boat upstream = (x - y) km/h
Given, boat takes 2 hours to go 40 km down the stream
⇒ 2(x + y) = 40
⇒ x + y = 20 …….(i)
Given, boat returns in 4 hours
⇒ 4(x - y) = 40
⇒ x - y = 10 …….(ii)
Adding (i) and (ii) we get,
⇒ (x + y) + (x - y) = 20 + 10
⇒ 2x = 30
⇒ x = 15.
Substituting value of x in (i) we get,
⇒ 15 + y = 20
⇒ y = 5.
Hence, speed of boat in still water = 15 km/h and speed of stream = 5 km/h.
Answered By
35 Likes
Related Questions
2 men and 5 women can do a piece of work in 4 days, while one man and one woman can finish it in 12 days. How long would it take for 1 man to do the work?
A train covered a certain distance at a uniform speed. If the train had been 30 km/h faster, it would have taken 2 hours less than scheduled time. If the train were slower by 15km/h , it would have taken 2 hours more than the scheduled time. Find the length of the journey.
A boat sails a distance of 44 km in 4 hours with the current. It takes 4 hours 48 minutes longer to cover the same distance against the current. Find the speed of the boat in still water and the speed of the current.
An aeroplane flies 1680 km with a head wind in 3.5 hours. On the return trip with same wind blowing, the plane takes 3 hours. Find the plane's air speed and the wind speed.