Question

Place a nd b ar 80 km apart each other on highway a car from a and other from b at same time if they move in same direction they meet in 8 hr and if move in oppo. Directions they meet in 1hr 20 min find speed of cars

Answer 1

w.k.t speed=distance/time.

let the speed of the car which is started from place a is A,and speed of the car which is started from place b is B.

in first case: if they are travelling in same direction then the relative speed of cars is A-B (where A>B).

speed A-B= 80/8 = 10 kmph..........[1]

in second case : if the cars are travelling in opposite in directions,then the relative speed of cars is A+B.

A+B= 80/(4/3) = 60 kmph.........[2]        ( 1hr 20 min is equal to 4/3 hours)

by solving equations [1],[2] we will get A=35 kmph

                                                               B= 25 kmph.

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