Aptitude - Time and Distance - Discussion

@ISHAN the speed of the car is 60km/hr.

1)Let the speed be x km/hr.

2)Given distance covers =420km we know time t= distance/speed.

3)So let t= 420/x.

4)Given if speed is 10km/hr more so time (t-1)= 420/(x+10).

We have considered t=t-1 above because they have mentioned 1hr less so 420/x - 420/(x+10)=(t-t-1) i.e total distance/totalspeed = time

5)By solving we get x^2+10x-4200=0 we get x=60 &-70 ignore -70... 60 is answer.

Time = distance / speed.

600 *30 /200.

30 * 3 = 90 total time.

Exact time = total time - increase time.

= 90 - 30.

= 60.

Still confuse about 600/x-600/(x+1/2) = 200. Please let me know something very simply.

Distance = 600 km.
Average speed = 200 km.

If time taken is x min therefore the increased value of time = (x+30)min = (x+30)/60 hrs.

So by applying the formula of speed i.e. S=D/T, we get,

600 km=200 kmph/((x+30)/60)hrs.

600km = 200kmph*60/(x+30).

(600x+ 1800)km = 1200kmph.

Now by leaving the units as they are hrs for time , we get,

600x= 1200-1800.
600x = -600.

x = -600/600.
x = -1.

Since time can never be negative, Therefore by leaving the negative sign we get, x=1 hr.

Generally time taken to travel 600 km with 200 kmph will take 3 hr journey but how the time of flight will be 1 hr.

@Sakshi.

2 mistakes done by you.

1. D= s*T , and you have taken d=s/t as 200 Kmph is speed.

2. How 200 kmph *200 = 1200? it should be 12000. The whole logic is wrong.

This type question take more time in competitive exam so we can go through the answer to question.

If we take 1 as answer.

600/x - 600/x+1/2 = 200.

Then we substitute x = 1.

Please solve anyone this equation 600/x-600/x+1/2=200 I can't understand.

Please solve this equation 600/x-600/x+1/2=200 I can't understand. As it followed a long solution.

@Aarman and @Swetha.

(600/x)-(600/(x+1/2)) = 200
=> (600/x)-((600*2)/2x+1)) = 200
=> (600/x)-((1200)/2x+1)) = 200;

==>(600(2x+1)-1200x)/(x(2x+1)) = 200;
==>(1200x+600-1200x)/(2x^2+x) = 200;

==> (600)/(2x^2+x) = 200;
==> 600 = 400x^2+200x;

==> 400x^2+200x-600 = 0;
==> 200(2x^2+x-3) = 0;

==> 2x^2+x-3 = 0;
==> 2x^2+3x-2x-3 = 0;

==> x(2x+3)-1(2x+3) = 0;
==> (2x+3)(x-1) = 0;

So x=-3/2; x=1;

Since time can never be negative, Therefore by leaving the negative sign we get, x=1 hr and x=3/2 hr.