speed , time and distance

Question

Point X and Y are 90 km apart from each other at highway. A car starts  from X and another from Y at the same time . If they go in the same direction  they meet in 9 hrs and if they go in opposite direction they meet in 9/7 hrs. The max speed of the car among the 2 cars is

a)20 km/hr

b)30 km/hr

c)40 km/hr

d)50 km/hr

Answer 1

Let both the vehicles having X km/hr and Y km/hr speed.

If they go in same direction their relative speed will be X-Y (assuming X > Y)

So, speed = distance/time

X-Y = 90km / 9hr

X-Y = 10km/hr

If they go in opposite direction their speeds will be added.

X+Y = 90km / (9/7)hr

X+Y = 70km/hr

Solving these two equations, we will get

X = 40Km/hr and Y = 30Km/hr.

So answer is Option C.

Answer 2

x + y= 90/9

x-y=90*7/9

solve eqn

x= 40

y=30

so ans is 40