Question

A person travels one-third of the total distance at a speed of 2 km/h, the next one third of the total distance at a speed of 3 km/h and the rest of the total distance at a speed of 6 km/h. Find the aver- age speed of the person for the total trip​

Answer 1

Answer:

The time taken by the boy to cover a certain distance = 1 hour 24 minutes

The speed of covering two-thirds distance = 4 km/h

The speed of covering the rest of the distance = 5 km/h

Formula used:

T = D/S

where, T = time of the journey, S = speed, D = distance travelled

Calculation:

Let the total distance be 3D km.

The two-third distance of 3D = (2/3) × 3D = 2D km

Remaining distance

The One-third distance of 3D = (1/3) × 3D = D km

Time taken for covering 2D distance = (2D/4) hour

Time taken for covering rest distance = (D/5) hour

According to the question,

(2D/4) + (D/5) = 1 h 24 min

⇒ (D/2) + (D/5) = 1 + (24/60)

⇒ (5D + 2D)/10 = 1 + (2/5)

⇒ 7D/10 = 7/5

⇒ D/2 = 1

⇒ D = 2 km.

Now, total distance = 3 × 2 = 6 km