## Study notes on Speed, Time and Distance for DSSSB Exam

Dear Readers,

Here we are providing you Study notes on Speed, Time and Distance which will be helpful for Upcoming CTET and DSSSB Exams.

Some memorable points and facts regarding speed, time and distance:-

1. Distance = Speed x Time

2. Time = Distance/Speed

3. Speed = Distance/Time

4. If speed is given in kilometre per hour then in order to convert it into metre per second, it is multiplied by 5/18. Suppose speed is x km/h then speed in (x * 5/18) m/s will be.

5. If speed is given in metre per second then in order to convert it into kilometre per hour, it is multiplied by 18/5. Suppose speed is x m/s then speed in km/hr will be

(x * 18/5) km/hr

6. Suppose a man covers a distance at x km/hr and an equal distance at y km/hr. Then, average speed during whole journey = 2xy/(x+y)km/h.

7. If the ratio of speeds of A and B is x:y, then the ratio of times taken by them to cover the same distance is 1/x:1/y.

8. If the time is constant, then speed is directly proportional to distance. Suppose speed is doubled, the distance travelled in the same time will also be doubled.

9. If speed is constant, the distance and time are directly proportional. Suppose distance is doubled, then it will take double time at the same speed.

10. If the distance remains constant, then time is inversely proportional to speed. Suppose speed is doubled, the time taken to travel the same distance will become half of the original time taken at the original speed.

11. If two persons start at the same time from two points A and B towards each other and after crossing they take ‘’ and ‘b’ hours in reaching B and A respectively.

Then, A’s speed: B’s speed = √a:√b

12. If a man covers three equal distance at x km/h, y km/h and z km/hr. respectively, then the average speed of the whole journey is given by 3xyz(xy+yz+zx).

Illustrations based on above mentioned memorable points

Example - (1) : Convert 90 km/hr into metre / sec.

Solution: As per memorable point 4.

Speed in m/s = 90 nx(5/18)

= 25 m/s.

Example - (2) : Convert 15 metre / sec. into km/hr.

Solution: As per memorable point 5

Speed in km/h = 15 x (18/5)

= 3x 18 km/hr. = 54 km/hr.

Example - (3) A person crosses a 1200 metre long street in 5 minutes. What is his speed in km per hour?

Solution :

We are given Distance = 1200 metre

Time = 5 minutes = 300 seconds.

Speed =1200/300 = 4m/sec.

Speed in km/hr = 4 x(18/5)

=14.4 km/hr

.

Example (4): An aeroplane covers a certain distance at a speed of 240 km/hr in 10 hours. To cover the same distance in hours, at what speed it must travel.

Solution: We have

Speed (s) = 240 kmph.

Time (t) = 10 hours

Distance = 240x10=2400 km.

## Quant Quiz on Speed, Time and Distance for DSSSB Exam

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**Team Clear IBPS**