**Speed**

The distance travelled or covered by a person or object in unit time, is called its speed.

**Time**

The duration in hours, minutes or seconds spent to cover a certain distance is called time.

**Distance **

The length of path which covered by a person or object between two places, is known as distance. The unit of distance is m or km.

**Average Speed**

Average speed of an object is defined as total distance travelled divided by total time taken.

## Important Formulae

### Formula 1

**If an object covers same distance with speed of x km/h and y km/h respectively, then average speed of object will be**

**Ex. A train covers a distance between A and B with speed 60 km/h and returned from B to A with speed 40 km/h The average speed of train for complete journey will be**

(a) 42 km/h

(b) 50 km/h

(c) 48 km/h

(d) None of these

### Formula 2

**Ex:A man covers a distance between his house and office by scooter. If he drives with speed 60 km/h , he lates by 20 min and if he drives with speed 80 km/h, he reached early by 10 min. The distance between his house and office is**

(a) 90 km

(b) 60 km

(c) 120 km

(d) None of these

### Formula 3

** When two persons A and B start at the same time from two points P and Q towards each other and after crossing each other, they take a h and b h in reaching Q and P, respectively. Then,**

** Ex:A man sets out to cycle from point P to Q and at the same time, another man starts to cycle from point Q to P. After passing each other, they complete their journeys in 9 h and 4 h respectively. What is the ratio of speeds of 1st man to that of 2nd man?**

(a) 3:1

(b) 6:4

(c) 2:3

(d) None of these

### Formula 4

** If a train passes a still object like tree, pole etc, train has to travel a distance equal to its length. If a train passes a long object like platform, bridge etc, train has to travel a distance equal to sum of length of object and that of train.**

**Ex:A train passes a man standing on a platform in 8 sec and also crosses the platform which is 264 m long in 20 s. The length of the train (in m ) is**

(a) 188

(b) 176

(c) 175

(d) 96