Question

Two places A and B are 80km apart from each other on a highway. a car starts from A and another from B at the same time. If they move in the same direction, they meet in 8 hours and if they move in opposite directions they meet in 1 hour and 20 minutes. find the speed of the cars

Answer 1

Hi,


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

We know that,
______________________
Time = distance / speed
______________________

Distance between two places A and

B 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

Therefore ,

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

Speed of the second car = 25km /hr

I hope this helps you.

:)

Answer 2

let the speed of the car at A be x km/ h
and the speed of the car at B be y km/ h
case 1 8x-8y=80
x-y=10
case 2 4/3x + 4/3y = 80
x+y = 60
on solving x = 35 and y = 25
hence, speed of the cars at A and B are 35 km/h and 25 km/h respectively.

i hope this helps you
plz mark it as brainlyest answer