Question

A car travels from city A to city B, 120 km apart at an average speed of 50 km/h. It then makes a return trip at an average speed of 60 km/h. It covers another 120 km distance at an average speed of 40 km/h. The average speed over the entire 360 km will be ?

Answer 1

Given :-

• Car Travel from city A to city B, 120 km apart at an average speed of 50 km/h.
• return trip at an average speed of 60 km/h.
• It covers another 120 km distance at an average speed of 40 km/h..

To Find :-

• Average Speed of Whole Journey . ?

Solution :-

→ Distance From city A to B = 120km .

→ Average Speed = 50km/h.

→ So, Time Taken by car = (Distance/Speed) = (120/50) = (12/5) hours. ------------- Equation (1).

_________________

Now,

→ Return Trip distance = 120km.

→ Average Speed = 60km/h.

→ So, Time Taken by car = (Distance/Speed) = (120/60) = 2 hours. ------------- Equation (2)

_________________

And,

→ Another Distance = 120km .

→ Average Speed = 40km/h.

→ So, Time Taken by car = (Distance/Speed) = (120/40) = 3 hours. ------------- Equation (3)

_________________

So,

→ Total Distance = 120 + 120 + 120 = 360km.

→ Adding All equation, Total Time = (12/5) + 2 + 3 = (12/5) + 5 = (12 + 25)/5 = (37/5) Hours.

So,

→ Average Speed of Entire Journey = (Total Distance)/(Total Time) = (360)/(37/5) = (360*5)/37 = 48.64km/h.

Hence, The average speed over the entire 360 km will be 48.64km/h.

Answer 2

$\huge{\purple{\bf{QuEsTion}}}$

A car travels from city A to city B, 120 km apart at an average speed of 50 km/h . It then makes a return trip at an average speed of 60 km/h. It covers another 120 km distance at an average speed of 40 km/h . The average speed over the entire 360 km will be?

$\huge{\purple{\bf{SoluTion}}}$

using , time = distance / speed

• Time taken by Car to travel 120 km with speed of 50 km/h will be

t₁ = 120 / 50

$\bf{t_1=\frac{12}{5}\:h}$

• Time taken by Car to cover 120 km with speed 60 km / h during return trip

t₂ = 120 / 60

$\bf{\t_2=2\:h}$$\bf{t_2=2\:h}$

• Time taken by Car to cover another 120 km with speed 40km/h

t₃ = 120 / 40

$\bf{t_3=3\:h}$

Now,

total distance covered by car = 3 (120) km = 360 km

total time taken for journey = t₁ + t₂+t₃

total time taken = ( 12/5)+2+3 = 37/5 h

so,

average speed = total distance / total time

average speed = 360 / (37/5)

average speed = 360*5/37

average speed = 48.64 km/h. (Ans.)