Question

A body covers 100 km in 2 hours. If in first one hour body covers 40 km, then the average speed of the body in next one hour
is
O 50 km/h
o 40 km/h
O 80 km/h
O 60 km/h​

Answer 1

Solution :-

Given that

• Distance covered by the body in 2 hrs = 100 km
• Distance covered in first hour = 40 km

To find,

• Average speed of the body in next hour

_______________________

Firstly finding total average speed & average speed of the first hour

Average speed = Total distance/total time

Avg speed = 100/2 = 50 km/h ………(Total avg speed)

Avg speed = 40/1 = 40 km/h ………(Avg speed first hour)

Now , finding average speed of the body in next hour . Using ,

Average speed = 2V1V2/V1 + V2

50 = 2(40)V2/40 + V2

50 = 80V2/(40 + V2)

80V2/50 = 40 + V2

8V2/5 = 40 + V2

8V2/5 - V2 = 40

3V2/5 = 40

V2 = 40 × 5/3

V2 = 200/3

V2 = 66.66 km/h.

Hence , average speed for next one hour = 66.6 km/h

Answer 2

Explanation:

Solution :

• Given that

Distance covered by the body in 2 hrs =100 km Distance covered in first hour = 40 km

• To find,

Average speed of the body in next hour

• formula used:

Average speed = Total distance/total time

___________________________________________

Averag speed = 100/2 = 50 km/h.......(total)

Averag speed(1)= 40/1 = 40 km/h .........(first hour)

let 2 nd average speed = V2 km/h.........(Second hour)

___________________________________________

Now , finding average speed of the body in next hour. Using,

Average speed = 2V1V2/V1 + V2

$50 = \frac{2(40)V2}{40 + V2}$

$50 = \frac{80V2}{(40 + V2)}$

$\frac{80V2}{50} = 40 + V2$

$\frac{8V2 }{5} = 40 + V2$

$8V2/5 - V2 = 40$

$\frac{8V2}{5} = 40$

$V2 = 40 \times \frac{5}{8}$

$V2 = 25 km/h.$

Hence , average speed for next one hour = 66.6 km/h