Question

15. 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.

Answer 1

Answer:

Step-by-step explanation:

Let the speed of car starting from A be 'x' km/h and speed of car starting from B be 'y' km/h.

Total distance=80 km

Also 1 hour 20 mins= 4/3 hour

As per given condition, When car moves in same direction,

Distance travelled by y= 8y km

Distance travelled by x= 8x= 80+8y

Now, Equation formed is 8x=80+8y

=> 8x-8y=80

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

Similarly, For opposite direction,

Distance travelled by x= (4/3)x

Distance travelled by y= (4/3) y

Also total distance covered= 4/3*x+4/3y

=> 80= 4x+4y/3

=> 240= 4x+4y

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

Solving Equation (1) and (2)

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

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

=> x= 10+y ----(3)

Substituting the value of (3) in (2) we get,

60= 10+y+y

=> 60-10=2y

=> 50=2y

=> 25=y

Also, x=10+y=> x= 10+25=> x=35

Therefore Speed of car starting from A is 35km/h

Speed of car starting from B is 25km/h

Answer 2

Answer:

Speed of Car A  and B are 35 km / hr and 25 km / hr respectively.

Step-by-step explanation:

Let the speed of car at A is x km / hr and at B is y km / hr

Case 1.

8 x - 8 y = 80

x - y = 10

x = 10 + y ... ( i )

Case 2.

4 / 3 x + 4 / 3 y = 80

x + y = 60

x = 60 - y ... ( ii )

From ( i )  and  ( ii )

10 + y = 60 - y

y = 25

Putting value of y in ( i )

x = 10 + 25

x = 35 .