Time and Distance:

It is important to know the relation between Time, Distance and Speed.

1. Speed is defined as the distance covered by an object in one unit of time.

Speed = (Distance / Time)

Distance = Speed * Time

Time = (Distance / Speed)

2. Below formulae for converting Km/h to m/s and m/s to km/h

=> X km/h = {X * (5 / 18)} m/s

=> X m/s = {X * (18 / 5)} km/h

3. If the two objects are moving with X and Y speeds respectively, then

Relative speed = X + Y (If the two objects are moving in opposite direction)

Relative speed = X – Y (If the two objects are moving in same direction)

4. If the ratio of speeds of X and Y is A : B, then the ratio of time taken to cover the same distance is B : A

Previous year solved Questions:

1. A van covers a distance of 690 km in 30h. What is the average speed of the car?

A) 25 km/h B) 23 km/h C) 20 km/h D) 18 km/h E) None of these

Ans: B

Solution: Using the formulae, Speed = (Distance / Time)

=> (690 / 30) = 23 km/h

2. A certain distance is covered at a certain speed. If half of the distance is covered in double time, what is the ratio of the two speeds?

A) 4 : 1 B) 1 : 4 C) 1 : 2 D) 2 : 1 E) 1 : 1

Ans: A

Solution: Let assume certain distance = X km, X km covered in Y hr.

Then speed = (X / Y) km/h

If the distance is covered in double time = {(X / 2) / 2Y} = (X / 4Y) km/h

Then required ratio is (X / Y ) : (X / 4Y) = 4 : 1

3. A bike runs at the speed of 50 km/h when not serviced and runs at 60 km/h when serviced. After servicing the bike covers a certain distance in 6 h. How much time will the car take to cover the same distance when not serviced?

A) 8.2h B) 6.5h C) 8h D) 7.2h E) None of these

Ans: D

Solution: From the given data, after servicing speed of the bike = 60 km/h

Distance covered in 6h. = (60 * 6) km = 360km

When it’s not service,the time taken to cover 360 km = (360 / 50) = 7.2h