# Time, Speed & Distance: Basic concept and Shortcut tricks

**Speed**: Speed is nothing but the rate at which certain distance is covered. Thus the basis relationship between time, speed and distance is

**Speed= Distance covered/ Time taken**

Unit of speed will be either in meter/sec or km/hour.

1 km/hr=5/18meter/sec

1 meter/sec=18/5 km/hr

For **Example**: If A person moves from A to B travelling at distance of 10 km in 4 hours.

Then applying above formula

Speed= 10km / 4hr

= 2.5 km/hr

It means person is able to move 2.5 km in every 1 hour.

In the same problem if person moving form Delhi to Haryana at speed of 2.5 km/hr in 1 day 10 hr then

**Distance travelled = speed x time**

Distance= 2.5km/hr x (1 day +10 hr)

=2.5 x 34

= 85 km

So we can find from above formula that

Speed is directly proportional to distance. Thus if twice the distance is covered is same time then speed will be twice.

Speed is inversely proportional to time. If speed becomes x time then time taken to cover the same distance will become 1/x times.

**S1T1=S2T2=S3T**3………

Wher S1, S2, S3……… are speeds

T1, T2, T3 …..are time taken to travel the same distance

Distance is directly proportional to time taken. Thus time taken at same speed becomes 1/xth, it means distance has become 1/xth.

If certain distance is covered at x km/hr and same distance is covered at y km/hr then average speed during whole journey=

If three equal distances are covered at three different speeds x, y and z km/h, then average speed during whole journey is given by

If two persons A and B Starts at the same time in opposite directions from two points, and after passing each other they complete the journeys in ‘a’ and ‘b’ hrs respectively, then

**A’s Speed: B’s Speed=√b:√a**