Question

tell me the solution of this question

Answer 1

Let the distance from A to B is 'S'.

From A to B,

Distance = S

Average speed = 40 km/h

Let the time taken is T1.
Using formula,

⇒ Average Speed = Distance ÷ Time

⇒ 40 km/h = S ÷ T1

⇒ ( 40 km/h ) T1 = S

⇒ T1 = S ÷ ( 40 km/h )

⇒ T1 = Sh/40 km

From B to A,

Distance = S

Average speed = 50 km/h

Let the time taken in T2.

Using formula,

⇒ Average Speed = Distance ÷ Time

⇒ 50 km/h = S ÷ T2

⇒ ( 50 km/h ) T2 = S

⇒ T2 = S ÷ ( 50 km/h )

•°• T2 = Sh/50 km

Now for total journey,

Distance = S + S = 2S

Total time = ( Sh/40 km ) + ( Sh/50 km )

= ( 5Sh + 4Sh ) / 200 km

= 9Sh/200 km

Using formula,

⇒ Average Speed = Total Distance ÷ Time

= 2S ÷ ( 9Sh/200 km )

= 2S × ( 200 km / 9Sh )

= 400 km / 9 h

= 44.4444......... km/h

= 44.45 km/h ( Approx )

Answer 2

let the distance be X
CASE-1
DISTANE =X
SPEED=40 KM/HR
TIME=DISTANCE/SPEED
=X/40HR
CASE-2
DISTANCE IS SAME =X
SPEED= 50KM/HR
TIME=DISTANCE/SPEED
=X/50HR

AVERAGE SPEED= TOTAL DISTANCE/TOTAL TIME

=X+X/X/40+X/50
TAKING LCM OF 40AND 50

=2X /5X+4X/200
RECIPROCAL,
= 2Xx200/9X
X IS CANCEL
= 2x200/9
= 400/ 9
=44.4km/hr