Water current speed.

Two cities along the river are 100 km apart. The powerboat downstream runs for 4 hours, upstream for 10 hours. Determines the river's current speed.

Result

v =  7.5 km/h

Solution:


100 = 4*(a+v)
100 = 10*(a-v)

4a+4v = 100
10a-10v = 100

a = 352 = 17.5
v = 152 = 7.5

Calculated by our linear equations calculator.







Leave us a comment of example and its solution (i.e. if it is still somewhat unclear...):

Showing 0 comments:
1st comment
Be the first to comment!
avatar




To solve this example are needed these knowledge from mathematics:

Looking for help with calculating harmonic mean? Looking for a statistical calculator? Do you have a system of equations and looking for calculator system of linear equations? Do you want to convert length units?

Next similar examples:

  1. Walkers
    chodci From points A and B simultaneously started against each other two walkers. After meeting both continue to B. Second walker came to B 2 hours before the first walker. It's speed is 2.7 times of speed of the first pedestrian. How many hours went pedestria
  2. Two planes
    aircraft2 Two planes flying from airports A and B, 420 km distant against each other. Plane from A took off 15 minutes later and flies at an average speed of 40 km/h higher than the plane from B. Determine the average speed of this two aircraft if you know that it
  3. Aircraft nose down
    stall_747 How long will fall airliner from a height of 10000 m at speed 1,000 km/h?
  4. Aircrafts
    boeings Above the town hall tower flew the plane with constant speed 592 km/h and 15 minutes later the second plane at speed of 675 km/h. How long and how far from the town hall will be aircrafts caught up?
  5. Skier
    skiing_1 At this point, the first skier lead 20 km before the second skier and travels at a constant speed 19 km/h. The second skier rides at 24 km/h. How long take him to catch up the first?
  6. Truck PRG-BA
    kamionka Truck driving on highway from Prague to Bratislava at average speed of 72 km/h. At the moment when the truck passes 54 kilometer from Prague passenger car departs from Prague which travel to Bratislava at speed 90 km/h. When and where (at waht highway ki
  7. Blackjack TU160
    tu160 Bomber Tupolev TU160 started at 9:00 from the airport and flew at average speed of 1850 km/h toward the airfield B distant 3500 km. After evaluating the danger from the airport B started at 9:45 B towards A fighter MIG 29 at an average speed 2300 km/h. At
  8. Trains
    trains_toys From station 130 km away started passenger train and after 2.2 hours after the express train, which travels 37 km an hour more. Express train finish journey 7 minutes early. Calculate the average speed of this two trains.
  9. Wavelength
    wave_length Calculate the wavelength of the tone frequency 11 kHz if the sound travels at speeds of 343 m/s.
  10. Cyclist vs car
    car2 Cyclist rode out of the city at 18 km/h. 1 hour 30 minutes behind him started car and caught up with the cyclist in 50 minutes. How fast was driving the car? Where (what kilometer) from the city car overtook a cyclist?
  11. Theorem prove
    thales_1 We want to prove the sentense: If the natural number n is divisible by six, then n is divisible by three. From what assumption we started?
  12. Linsys2
    linear_eq_3 Solve two equations with two unknowns: 400x+120y=147.2 350x+200y=144
  13. Father 7
    family_8 Father is 6 times older than his son. After 4 years, the father will only be 4 times older. What are their present ages?
  14. Pooja
    clocks_14 Pooja and Deepa age is 4:5, 4 years back it was 8:11. What is the age of Pooja now?
  15. Family
    4kids Family has 4 children. Ondra is 3 years older than Matthew and Karlos 5 years older than the youngest Jane. We know that they are together 30 years and 3 years ago they were together 19 years. Determine how old the children are.
  16. Sebastian
    cool From Kovalov Sebastian walks at 6 km / h started at 8:00 in the direction of Kuty. From Kuty, the godfather is driving at 50 km/h and started at 8:30. The distance is 24 km. When and where grandfather will take Sebastian to the car.
  17. Three workshops
    workers_24 There are 2743 people working in three workshops. In the second workshop works 140 people more than in the first and in third works 4.2 times more than the second one. How many people work in each workshop?