The boat sailed 24 km along the river and 105 km against the river in 3 years.

| May 1, 2021 | education

The boat sailed 24 km along the river and 105 km against the river in 3 years. Know the speed of the current if the boat’s own speed is 45 km / h.

The sought speed of the river is denoted by the conditional variable “Y”.

At the second stage, applying the speed formula, we get this equation: 24 / (45 + Y) + 105 / (45 – Y) = 3.

As a result of solving this equation, we get 24 x (45 – Y) + 105 x (45 + Y) = 3 x (45 – Y) x (45 + Y) or 1080 – 24Y + 4725 + 105Y = 3 x (2025 – Y ^ 2) or 5805 + 81Y = 6075 – 3Y ^ 2 or 3Y ^ 2 + 81Y + 5805 – 6075 = 0 or 3Y ^ 2 + 81Y – 270 = 0 or Y ^ 2 + 27Y – 90 = 0 or Y1,2 = (-27 +/- √ ((- 27) ^ 2 – 4 x (-90))) / 2 = (-27 +/- √ (729 + 360)) / 2 = (-27 +/- √1089 ) / 2 = (-27 +/- 33) / 2 = 6/2 = 3 kilometers per hour or -60/2 = -30 kilometers per hour.

Since the speed is positive, the correct answer is 3 kilometers per hour.

Answer: 3 kilometers per hour.



One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.