Question

point A and B are 80 km apart on a highway 1 car starts from A and another from B at the same time if the car travel in the same direction at different speed they meet in 8 hours if they travel towards Each Other they meet in 1 hour 20 minute what are the speed of the two cars?

Answer 1

LET THE SPEED OF 1 CAR BE X & OTHER BE Y

DIST COVERED BY A IN 5 HR. = 5 * X = 5X

DIST COVERED BY B IN 5 HR = 5Y

A/Q WHEN THEY TRAVEL IN SAME DIRECTION

THEN 5X - 5Y = 100 => X -Y =20 .....(!)

NOW, DIST COVERED BY A IN 1 HR = X

DIST COVERED BY B IN 1 HR = Y

WHEN THEY TRAVEL TOWARDS EACH OTHER

THEN

A/Q, X +Y =100 ......(2)

NOW (!) - (2) = ( X -Y)-( X +Y)=20 - 100

=> 2Y = 80 HENCE Y = 40 KM /HR.

AND X= 20 +Y = 60 KM/HR

Answer 2

Let the speed of the first car which starts from A = x km /hr

Speed of the second car which starts from B = y km / hr

Time = distance / speed

Distance between two places A andB are 80km d = 80 km

i ) if the cars move in same direction

Relative speed of them = ( x + y )km/hr

Time = 8hr

d = 80km

8 = 80 / ( x + y )

x + y = 80 / 8

x + y = 10 ------( 1 )

ii ) if two cars moving opposite direction, Relative speed = ( x - y ) km / hr

Time = 1 hr 20 minutes

= ( 1 + 20 / 60 ) hr

= ( 80/60)

= 4/3 hr

d = 80km

4/3 = 80 / ( x -y )

x -y = ( 80 × 3 ) / 4

x - y = 60-----( 2 )

Add ( 1 ) and ( 2 ) , we get

2x = 70

x = 35

Put x = 35 in ( 1 ) we get ,

y = 25

so,

Speed of the first car = x = 35km/hr

Speed of the second car = 25km /hr

hope it helps you mark as brainliest please