Question

A car covers 40 km in first hour, 20 km in next hour and 30 km in third hour, what is its average speed
(A)20 kmph
(H) 30 kmph
(C)40 kn
Di None of these​

Answer 1

avg speed is equal to total distance upon time

given

1st hour 40 km distance

2nd hour 20 km distance

3rd hour 30 km distance

now total time = 3 hrs

now total distance = 90 km

avg speed = 90/3 = 30 km/ph

option H

Answer 2

Given:

1. 1st hr ⇒ 40 km
2. 2nd hr ⇒ 20 km
3. 3rd hr ⇒ 30 km

To Find:

The average speed of the car throughout the journey

Solution:

Average speed refers to the ratio of the total distance travelled by the object to the time taken for it to cover the distance.

It can be summarised by the formula:

Average Speed (S) =

Total distance travelled by the object (d) ÷ time taken to cover the distance (t)

$S = \frac{d}{t}$

Now, find the values of d and t

• Total distance travelled by the object (d) =

        40km + 20km + 30km =

        90km

• Time taken to cover the distance (t) =

        1 + 1 + 1 =

        3 hrs

We know,

d = 90km

t = 3 hrs

Put the values in the above formula to find S

$S = \frac{d}{t}$

$S=\frac{90}{3}$

$S= 3km/h$

(no need to convert quantities as the units match with the units of the options provided)

Hence, the average speed of the car is $3km/h$.