Question

ABCD is a straight line such that AB = BC = CD . A car travelled with a speed of 40kmph from A to B and with speed of 60kmph From B to D . it's average speed in kmph in the journey

i) From A to C
ii ) From A to D

Answer 1

Answer:

see attachment for explanation

Explanation:

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Answer 2

Solution:

Let time taken by the car from

• A - B → t1
• B - C → t2
• C - D → t3

AB = BC = CD be 'd'

That means

• AB = d , BC = d , CD = d. [°.° All distances are equal ]

Now , finding time using

Time = Distance/speed

→ t1 = d/40

→ t2 = d/60

→ t3 = d/60

________________________

Now. coming to the question

Distance from A - C = AB + BC = d + d = 2d

Distance from A - D = AB + BC + CD = 3d

Average speed = Total distance/total time

i) Average speed (A - C) = 2d/t1 + t2

→ Avg speed (A - C) = 2d/(d/40 + d/60)

→ Avg speed (A - C) = 2d/(3d + 2d/120)

→ Avg speed (A - C) = 2d/(5d/120)

→ AVg speed (A - C) = 240d/5d

→ Avg speed (A - C) = 48 km/h

ii) Average speed (A - D) = 3d/t1 + t2 + t3

→ Avg speed (A - D) = 3d/(d/40 + 2d/60)

→ Avg speed (A - D) = 3d/(3d + 4d/120)

→ Avg speed (A - D) = 3d/(7d/120)

→ Avg speed (A - D) = 360d/7d

→ Avg speed (A - D) = 51.4 km/h

Answers :

i) answer = 48 km/h

ii) answer = 51.4 km/h