Question

A car travels 30 km at a
uniform speed of 40 km/h
and the next 30 km at a
uniform speed of 20 km/h.
Find the average speed......​

Answer 1

Answer:

• Average speed of car = 26.66 km/hr.

Explanation:

Given:

• A car travels 30 km at a uniform speed of 40 km/h.
• Same car travels next 30 km at uniform speed of 20 km/h.

To Find:

• Average speed.

Now, we know that

=> Average speed = Total distance/Total time ......(1)

Now, Total distance = 30 + 30 = 60 km

Total Time = ?

Now, we will calculate time,

Case - 1). At uniform Speed of 40 km/h.

=> Speed = Distance/time

=> Time = distance/speed

=> Time = 30/40

=> Time = 3/4 hrs

Case - 2). At uniform speed of 20 km/h.

=> Speed = Distance/time

=> Time = distance/speed

=> Time = 30/20

=> Time = 3/2 hrs.

Now, Total Time = 3/4 + 3/2

=> Total Time = 9/4 hrs.

=> Total time = 2.25 hrs.

Now, we will put all the values in equation (1), we get

=> Average speed = total distance/total Time

=> Average speed = 60/2.25

=> Average speed = 26.66 km/hr (Approx).

Hence, Average speed of car = 26.66 km/hr (Approx).

Answer 2

☯ GiveN :

• A car travels 30 km at a uniform speed of 40 km/h.

• the next 30 km at a
• uniform speed of 20 km/h.

$\rule{200}{1}$

☯ To FinD :

We have ro find the average speed of the car.

$\rule{200}{1}$

☯ SolutioN :

We know the formula to calculate the average speed,

$\large{\implies{\boxed{\boxed{\sf{Average \: Speed = \dfrac{Total \: Distance \: travelled}{Total \: time \: taken ....(1)}}}}}}$

→ For calculating the average speed firstly, we will calculate Total distance travelled and total time taken by the car.

$\rule{100}{2}$

Total Distance travelled = 30 + 30

Total Distance travelled = 60 km ....(2)

$\small{\star{\boxed{\sf{Total \: Distance \: travelled = 60 \: km}}}}$

$\rule{100}{2}$

Now, we will calculate total time taken by car.

We know that,

$\large{\implies{\boxed{\boxed{\sf{Total \: time \: taken = \dfrac{Distance}{Speed}}}}}}$

$\small{\sf{\dashrightarrow Total \: time \: taken = \frac{30}{40} + \frac{30}{20}}} \\ \\ \small{\sf{\dashrightarrow Total \: time \: taken = \frac{30 + 60}{40}}} \\ \\ \small{\sf{\dashrightarrow Total \: time \: taken = \frac{90}{40}}} \\ \\ \small{\sf{\dashrightarrow Total \: time \: taken = \frac{9}{4} \: Hrs}} \\ \\ \small{\star{\boxed{\sf{Total \: time \: taken = \frac{9}{4} \: Hrs ....(3)}}}}$

$\rule{200}{2}$

★ Fromn equation (2) and (3). Put value in equation (1).

$\small{\sf{\dashrightarrow Average \: speed = \dfrac{\dfrac{60}{9}}{4}}} \\ \\ \small{\sf{\dashrightarrow Average \: Speed = \frac{60 \times4}{9}}} \\ \\ \small{\sf{\dashrightarrow Average \: Speed = \frac{240}{9}}} \\ \\ \small{\sf{\dashrightarrow Average \: speed = 26.67}} \\ \\ \large{\implies{\boxed{\boxed{\sf{Average \: Speed = 26.67 \: Kmh^{-1} }}}}}$