The boy rode a bicycle at a speed of 24 km / h, and then walked at a speed of 4 km / h, what part of the entire path

| September 24, 2021 | education

The boy rode a bicycle at a speed of 24 km / h, and then walked at a speed of 4 km / h, what part of the entire path and what part of the entire time of movement did the boy ride if he covered 16 km in 2 hours?

Vv = 24 km / h.

Vp = 4 km / h.

t = 2 h.

S = 16 km.

Sv / S -?

Since the boy covered the distance S in time t, he moved with an average speed Vav = S / t.

Vav = 16 km / 2 h = 8 km / h.

The time of the boy’s entire movement, t, will be the sum of the cycling time tв and the walking time tп: t = tв + tп.

Cycling time is expressed by the formula: tv = Sv / Vv.

The time of movement on foot tp is expressed by the formula: tp = Sp / Vp = (S – Sv) / Vp.

t = Sv / Vv + (S – Sv) / Vp.

t = (Sv * Vp + (S – Sv) * Vv) / Vv * Vp.

Sv * Vp + (S – Sv) * Vv = Vv * Vp * t.

Sv * Vp + S * Vv – Sv * Vv = Vv * Vp * t.

Sv * Vp – Sv * Vv = Vv * Vp * t – S * Vv.

Sv = Vv * (Vp * t – S) / (Vp – Vv).

Sw = 24 km / h * (5 km / h * 2 h – 16 km) / (4 km / h – 24 km / h) = 7.2 km.

Sw / S = 7.2 km / 16 km = 0.45.

Answer: 45% of the whole way the boy rode a bicycle, 55% walked: Sv / S = 0.45.



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.