Aptitude - Time and Distance - Discussion

Take one option 5hrs if Abhay goes with 5km/hr then it will take 6 hours to reach means 4 hours for Sameer. If he doubles his speed means 30/10 = 3kmph and as usual Sameer speed is 4kmph so the right answer is A.

Thanks, @Prakash. Understood the common factor.

Let the speed of Abhay be X kmph.
Let the Time taken by Sameer to cover a distance of 30 km be T hr.
According to problem;

Abhay takes 2hr more than Sameer i.e, (T+2)
Speed =Distance/Time .
Abhay's speed = total distance/ time taken by Abhay.

X=30/(T+2) --------> eqn1.

Now,
If Abhay doubles his speed i.e, 2X he would take 1 hr less than Sameer i.e (T-1)
2X=30/(T-1)--------> eqn1.

Now divide eqn1/ eqn2.
You will get T = 4hr.
Now put T=4 in eqn1. You will get X = 5kmph.

Thanks @Devi. Superb explanation.

Superb explanation, Thanks @Devi.

Well explanation, Thanks @Devi.

Thanks all.

Thanks @Devi.

@All.

Simply, the solution is;

Abhay's doubled speed is = to the speed required to cover 30km in 3 hrs.
2x=30/3,
x= 10/2,
x= 5 km/hr,

Another way to solve is;
(30/x)-(30/2x) = 3.
30((1/x)-(1/2x)) = 3.
1/2x = 1/10.
2x = 10.
x = 5 km/hr.

Abhay speed is getting double it means it will become Sameer = 2 Abhay and let us take Abhay as x then sameer will become 2x then add speed x+2x = 3x.