Aptitude - Time and Distance - Discussion

Hello I'm not getting from were do that "3" comes in second line. Please explain.

Let the speed be x, we will move with Abhay only at the outset.

A/Q D=S*T or, 30 = (t+2)*x or, 30/x = t+2.

If he doubles his speed then,

30 = (t-1)*2x or, 30/2x = t-1.

REMEMBER t is the time taken by Sameer.

D/S = T => 30/x-30/2x = 3 => x = 5.

Let Sammeer original time = x.

Abhay speed: y = 30/x+2 (let Abhay speed be y, x+2 is written because Abhay takes 2 hrs more than Sammer). This equation can be derived when you analyses the first statement alone.

So, let y = 30/x+2....> (1).

Case 2:

Abhay doubles his speed.

2y = 30/x-1(x-1 is because Abhay takes 1 hr less than Sammer).

So, 2y = 30/x-1....> (2).

From (2) , get the value of x and substitute in (1) , you will get the value of why which is Abhay speed.

2y = 30/x-1.
2y(x-1) = 30.
x-1 = 30/2y.

So, x = (30/2y)+1.

Substitute the x value in (1).

y = 30/x+2.
y =30/((30/2y)+1)+2.
y = 5.

Then what is the speed of Sameer?

If suppose x speed abay cover in y+2 time.

Then 2x speed he covered in y-1. (here why is sameer to cover time).

Then different between time = (y+2) - (y-1) =3. So.

First covered time - second covered time = 3.

Distance = 30.

Abhay's normal speed = x.
Abhay doubles speed = 2x.
Sameer's time = t.

t+2 = 2 hrs + sameer's time.

t-1 = 1 hr less than sameer's time.

[30/x] - [30/2x] = [t+2] - [t-1].
[30/x] - [30/2x] = 3.

[1/x] - [1/2x] = 1/10.
(2-1) /2x = 1/10.

1/2x = 1/10.
2x = 10.

x = 5 km/hr.

Can any one use proper formula of maths to solve this question because it is all confusing?

Please explanation clearly.

Hey just stick with anyone solution then you will definitely sure about the solution, don't go for each and every solution. Because it will confuse you. And yes nice explanation by @Devi :).

How 3 comes?

Guys please solve this question by answer don't get confused.

Example: 1st option is 5 km/hr if we take then Abhaya speed 30/5 = 6 hr then Sameer has time 4 hr means Abay has 2 hr more then Sameer after then speed double means 10 km/hr, Abhay takes time 30/10 = 3 hr mean 1 hr less then Sameer. So 1st option is correct answer.