Aptitude - Time and Distance - Discussion

I don't understand why we subtract 30/x-30/2x? Please explain me.

Given:

d=30;
Sameer speed=s1;
Abay speed=s2;

Time taken for covering 30 km is =t;
Speed*time=distance
s1*t=30
s2*(t+2)=30 -----> 1
s2*(t-1)=30 -----> .2

Abay have a different speed.
when he travelled in speed 1 he needs two hours more to get the distance
when he travelled in speed 2 he needs 1 hour less then Sameer's speed to get the distance
So we need to find the difference of time for both speeds,
equation 1-2 provides the time different.
(30/s2)-(30/2s2) = (t+2)-(t-1),
(30/s2)-(30/2s2) = 3,
(15/s2) = 3,
s2=5.

Thanks for the given explanation @Sakshi.

How come 3 here?

30/x - 30/2x = 3.

Here why should we subtract 30/x - 30/2x and how we will get 3?

Please can anyone explain?

Thanks everyone for explaining.

How come 3 here? Please explain.

Abay = 2hour + Sameer, [you can analyze this equation by taking sameer=5, which gives Abay=7]

And; 2 * Abay = Sameer - 1, [similarly in this equation, suppose sameer=5, which results in Abay=4]

Both the equation satisfies the above statement.

Suppose Abhay's speed is -x km/h.
then suppose y is Abhays speed;
(y+2)-(y-1)=3.
30/x-30/2x=3.
(60x-30x)/2x=3.
Ans is 5km/h.

Abhay's difference in covering the distance after doubling the speed is 2+1 = 3 hrs.
So, Abhay's speed after doubling the speed is 30/3 = 10,
So, the current speed of Abhay is 10/2 = 5.