The boat travels 150 km downstream in 2 hours. Moving at the same speed relative to the water, the boat travels the same

| June 25, 2021 | education

The boat travels 150 km downstream in 2 hours. Moving at the same speed relative to the water, the boat travels the same path against the current in 3 hours. How much is the speed of the boat more than the speed of the river.

Let the speed of the boat – Vk, the speed of the current – Vt.

Travel time 150 km downstream:

t1 = 150 km / (Vk + Vt) = 2 h (1).

Travel time 150 km upstream:

t2 = 150 km / (Vk – Vt) = 3 h (2);

150 km = 2 h * Vk + 2 h * Vt (3);

150 km = 3 h * Vk – 3 h * Vt (4);

We divide (3) by 2, and (4) we divide by 3:

75 km = 1 h * Vk + 1 h * Vt (5);

100 km = 1 h * Vk – 1 h * Vt (6);

Subtract equality (5) from equality (6):

25 km = 2 h * VT

VT = 12.5 km / h.

We substitute the found flow velocity into (5):

75 km = 1 h * Vk + 1 h * 12.5 km / h;

75 km – 12.5 km = 1 h * Vk;

Vk = 62.5 km / h.

Vк – Vт = 62.5 km / h – 12.5 km / h = 50 km / h.

Answer: at 50 km / h.



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.