Aptitude - Time and Distance - Discussion

Hey guys!

Actually x=3/2 is the correct answer.
if new time = 1.5 hrs(i.e 3/2 hrs)
then original time=1.5-0.5(i.e 30 minutes)
=1 hr.

Then original speed = 600 kmph (since 600 km in an hr)
new speed = 600-200
= 400 kmph.

New time = 600/400
= 1.5 hrs (fits correctly with x=1.5 i.e our initial assumption).
Now,
x=1
original time =30 minutes= 0.5 hr
original speed = 600 kmph * 05 hr
= 1200 kmph
new speed = 1200-200
= 1000 kmph.

new time = 600/1000
= 36 minutes.

Since x=30 minutes; x is not equal new time.
so conclusion:- time =1.5 hrs (answer choices are incorrect).

S inversely proportional to time;

Time increases flight speed decreases
T1s1=T2S2
X*600=(x+30)400
6x=4x+120
X=60.

How 600/x-600/x+1/2=200?

Why we take the difference and why it equal to 200?

How 600/x-600/x+2=200?

Please explain this step.

Can anyone explain 1st step, I'm not understanding.

30 min =1/2 hr.
Now I take time T in hr.
According to the question..... Distance is same so,
Distance of Normal flight = Distance due to bad weather (reduce by 200 kmph).

We know, distance = time * speed.

T*600 = ( 600-200) (T + 1/2) ..... (600-200 bcz speed is reduce by 200 kmph).

600T = 400T +200.

T= 1 hr.

600(2x+1)-1200x=200x(2x+1).
1200x+600-1200x=400x^2+200x.
600=400x^2+200x,
300=200x^2+100,
3=2x^2+x,
2x^2+x-3=0.

Change in in speed i.e speed reduced by 200 kmph then change in time is 30 mnts.
If speed reduce to zero i.e by 600kmph. Time taken will be 90 mnts.

As mentioned in the question, Flight took 30 months more.
To find the original time of flight, 90 -30 = 60 months, i.e 1 hour.

Thanks @Kiran.

Let the time be x.

Total speed(Dis/time) - actual speed due to weather(dis/time) = reduced speed.

600/x - 600/ x+(1/2) = 200.
Here actual speed is less because of weather condition, which means it has taken MORE TIME which is 1/2 hour or 30 min.

Solve answer you get an answer as 1 hr.