Question

Places A and B are 80 km apart from each other on a highway. A car starts

from A and another from B at the same time. If they move in same direction

they meet in 8 hours and if they move towards each other they meet in 1 hour

20 minutes. Find the speed of cars by graphical method.​

Answer 1

Answer:

Let the speed of car starting from A=x km/hr and speed of car starting from B=y km/hr.

The relative speed of A with respect to B when moving in the same direction =x−y km/hr.

The relative speed of A with respect to B when moving in opposite direction =x+y km/hr.

Distance between A and B=80 km.

We know, Time=SpeedDistance

From the above information, we have,

x−y80=8andx+y80=1+6020=34

or,x−y80=8

⇒10=x−y

⇒x−y=10....(i)

Also,x+y80=34

⇒240=4(x+y)

⇒x=60−y....(ii)

Substituting (ii) in (i), we get,

x−y=10

⇒60−y−y=10

⇒60−2y=10

⇒2y=50

⇒⇒y=25

Substituting y=25 in equation (ii), we get,

x=60−y

⇒x=60−25

⇒x=35

Thus, the speed of car starting from A=x=35 km/hr and speed of car starting from B=y=25 km/hr.