Question

A car moves a distance of 200m . it covers the first half of the distance at speed 40kmperhr and second half of the distance at speed v . the average speed is 40kmperhr . the value of v is ?

Answer 1

Answer is v=60 km/h

48= 200/((100/40)+(100/v) )

or 1/40+1/v= 2/48=1/24

or 1/v=1/24-1/40=2/120=1/60

or v=60km/h

[Alt: v_av = (2v_1 v_2)/(v_1+v_2 ) => 48= (2×40×v)/(40+v) => v=60 km/h]

Answer 2

Answer:

The value of v is 40 km/hr.

Explanation:

Given that,

Distance = 200 m

Speed in first half = 40 km/hr

Average speed = 40 km/hr

We need to calculate the speed in second half

Using formula of speed

$v=\dfrac{D}{T}$

Where, D = total distance

T = total time

We divided the time in two equal parts

$T = t_{1}+t_{2}$

Using formula for time

The time in first half

$t_{1}=\dfrac{100}{40}$

The time in second half

$t_{2}=\dfrac{100}{v}$

$v=\dfrac{D}{t_{1}+t_{2}}$

Put the value of v,D, t₁ and t₂ into the formula of speed

$40=\dfrac{200}{\dfrac{100}{40}+\dfrac{100}{v}}$

$v=40\ km/hr$

Hence, The value of v is 40 km/hr.