Speed, Distance & Time Tips and Tricks
Table of Contents
We are providing you Important Short Tricks on Speed, Distance & Time which are usually asked in SSC Exams. Use these below given short cuts to solve questions within minimum time. These shortcuts will be very helpful for your upcoming SSC Exam 2016.
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Important formulae and facts of Time and Distance
Speed is a very basic concept in motion which is all about how fast or slow any object moves. We define speed as distance divided by time.
Distance is directly proportional to Velocity when time is constant.
- Speed Distance Time formula mathematically written as:- Speed = distance/time
Formula of Time :-time = distance/ Speed
So Formula of time is, time is equal to distance upon speed.
- Formula of Distance:-Distance = (Speed * Time)
Distance = Rate x Time
- To find rate, divide through on both sides by time:
Rate = Distance/Time
- Rate is distance (given in units such as miles, feet, kilometers, meters, etc.) divided by time (hours, minutes, seconds, etc.). Rate can always be written as a fraction that has distance units in the numerator and time units in the denominator, e.g., 25 miles/1 hour.
So distance is simply speed into time.
Note: All three formulae that formula of speed, formula of time and formula of distance are interrelated.
- Convert from kph (km/h) to mps(m/sec)
For converting kph(kilometre per hour) to mps(meter per second) we use following formula
x km/hr=(x∗5/18) m/sec
- Convert from mps(m/sec) to kph(km/h)
For converting mps(meter per second) to kph(kilometre per hour) we use following formula
x m/sec= X *(18/5) km/h
- If the ratio of the speeds of A and B is a : b, then the ratio of the times taken by then to cover the same distance is :1/a : 1/b or b : a
- Suppose a man covers a certain distance at x km/hr and an equal distance at y km/hr. Then,
the average speed during the whole journey is :- 2xy/(x + y)
- Relation between time, distance and speed: Speed is distance covered by a moving object in unit time: Speed= Distance covered/ Time Taken
Rule : 1: Ratio of the varying components when other is constant: Consider 2 objects A and B having speed Sa, Sb.
Let the distance travelled by them are Da and Db respectively and time taken to cover these distances be Ta and Tb respectively.
Let’s see the relation between time, distance and speed when one of them is kept constant
- When speed is constant distance covered by the object is directly proportional to the time taken.
ie; If Sa=Sb then Da/Db = Ta/Tb - When time is constant speed is directly proportional to the distance travelled. ie; If Ta=Tb then Sa/Sb=Da/Db
- When distance is constant speed is inversely proportional to the time taken ie if speed increases then time taken to cover the distance decreases. ie; If Da=Db then Sa/Sb= Tb/Ta
Rule 2: We know that when distance travelled is constant, speed of the object is inversely proportional to time taken
- If the speeds given are in Harmonic progression or HP then the corresponding time taken will be in Arithmetic progression or AP
- If the speeds given are in AP then the corresponding time taken is in HP
Distance Constant
- If distance travelled for each part of the journey, ie d1=d2=d3=…=dn=d, then average speed of the object is Harmonic Mean of speeds.
Let each distance be covered with speeds s1,s2,…sn in t1,t2,…tn times respectively.
Then t1 =d/s1
t2 = d/s2
tn =d/sn
then, Average Speed= [(d + d + d+ … ntimes)]/ [d/s1 + d/s2+ d/s3+ … d/sn
Average Speed= (n)/[(1/s1 + 1/s2+ …. 1/sn)]
Time Constant
- If time taken to travel each part of the journey, ie t1=t2=t3=…tn=t, then average speed of the object is Arithmetic
Let distance of parts of the journey be d1,d2,d3,…dn and let them be covered with speed s1,s2,s3,…sn respectively.
Then d1=s1 t , d2=s2t, d3=s3t, … dn=snt
then , Average Speed= [(s1/t+ s2/t+ …. sn/t)/(t + t+ … ntimes)]
Average Speed=( s1+ s2+s3+ … + sn)/n
Relative Speed
- If two objects are moving in same direction with speeds a and b then their relative speed is |a-b|
- If two objects are moving is opposite direction with speeds a and b then their relative speed is (a+b)
Some Question on Above formulas
Ques 1:– A man covers a distance of 600m in 2min 30sec. What will be the speed in km/hr?
Sol:: Speed =Distance / Time
=Distance covered = 600m, Time taken = 2min 30sec = 150sec
Therefore, Speed= 600 / 150 = 4 m/sec
= 4m/sec = (4*18/5) km/hr = 14.4 km/ hr.
Ques 2:– A car travels along four sides of a square at speeds of 200, 400, 600 and 800 km/hr. Find average speed.?
Sol: Let x km be the side of square and y km/hr be average speed
Using basic formula, Time = Total Distance / Average Speed
x/200 + x/400 + x/600 + x/800= 4x/y
=25x/ 2400 = 4x/ y
= y= 384
Average speed = 384 km/hr
Ques 3: A motor car does a journey in 10 hrs, the first half at 21 kmph and the second half at 24kmph. Find the distance?
Sol:
Distance = (2 x 10 x 21 x 24) / (21+24)
= 10080 / 45
= 224 km.
Ques 4:A boy goes to school at a speed of 3 kmph and returns to the village at a speed of 2 kmph. If he takes 5 hrs in all, what is the distance between the village and the school?
Sol : Let the required distance be x km.
Then time taken during the first journey = x/3 hr.
and time taken during the second journey = x/2 hr.
x/3 + x/2 = 5 => (2x + 3x) / 6 = 5
=> 5x = 30.
=> x = 6
Required distance = 6 km.
Ques 5: Walking ¾ of his speed, a person is 10 min late to his office. Find his usual time to cover the distance?
Sol : Usual time = Late time / {1/ (3/4) – 1)
= 10 / (4/3 -1 )
= 10 / (1/3)
= 30 minutes.
Most Important Questions with Short Tricks on Time, Speed and Distance
Question 1: A train running at 25 km/hr takes 18 seconds to pass a platform. Next, it takes 12 seconds to pass a man walking at 5 km/hr in the opposite direction. Find the sum of the length of the train and that of the platform.
(1) 125 m
(2) 135 m
(3) 145 m
(4) 155 m
Solution:
Speed of train = 25 km./hr.
Distance travelled in 18 secs at this speed
Where D = L . _{train} + L . _{platform}
length of train + length of platform = 125 m.
Short Trick:
Speed in m/sec.
Sum of length of train & Platform
Question 2: Two trains for Delhi leave Jaipur at 8.30 a.m. and 9.00 a.m. and travel at 60 km/hr and 75 km/hr respectively. How many km. away from Jaipur will the two trains meet.
(1) 125 km
(2) 150 km
(3) 175 km
(4) 200 km
Solution:
Distance covered by 1^{st} train in 30 min. = 30 kms. (as speed per hrs. 60)
Time taken by 2^{nd} train to cover 30 kms. = 2 hrs. (as it travels 15 km. per hr. more than 1^{st} train. Hence takes 2 hrs. to cover 30 km. that 1^{st} train has already covered)
Dist. covered = (60 x 2.5 hr.) or (75 x 2 hrs.) = 150 km.
Short Trick:
Required distance = (9.00 – 8.30) x
Question 3: Two places P and Q are 162 km apart. A train leaves P for Q and at the same time another train leaves Q for P. Both the trains meet 6 hrs after they start moving. If the train travelling from P to Q travels 8 km/hr faster than the other train, find the speed of the two trains.
(1) 17.5 km/hr, 9.5 km/hr
(2) 19.5 km/hr, 11.5 km/hr
(3) 21.5 km/hr, 13.5 km/hr
(4) Can’t be determined
Solution:
Suppose the speeds of the two trains are p km/hr and q km/hr respectively. Thus
and p – q = 8 …… (ii)
(i) + (ii) implies that
2p = 35 p = 17.5 km/hr
and (i) – (ii) implies that
2q = 19 q = 9.5 km/hr
Short Trick:
Take speed =
(x) + (x + 8) = 27 (as given diff. in speed = 8 kms./hr.)
9.5 & 17.5
Question 4: A train running at a speed of 60 kmph crosses a platform double its length in 32.4 seconds. What is the length of the platform?
(1) 180 metres
(2) 240 metres
(3) 360 metres
(4) 90 metres
Solution:
Let the length of the train be x m
length of the platform = 2x m
Total distance covered by the train = (2x + x =) 3x m
Now, according to the question
or,
Short Trick:
Speed in m/sec
Distance covered
Total length
540
(as the length of platform is double of the train)
Question 5: A train travels at the speed of 65 kms/hr and halts at 8 junctions for a certain time. It covers a distance of 1300 kms in 1 day (24 hours). How long does the train stop at each junction, if it halts for the same period of time at all the junctions?
(1) 30 minutes
(2) 20 minutes
(3) 60 minutes
(4) 40 minutes
Solution:
Speed = 65 kmph
Distance = 1300 kms
Time taken
Clearly, 4 hours are spent at 8 junctions in stoppages as one full day was taken for the journey to be completed.
Required time = 4 x 60 = 240 min. and at each junction the halt is of
Short Trick:
Time to cover 1300 km=D/S = 1300/65= 20 hrs
Break = 24 hrs. – 20 hrs. = 4 hrs.
Break at each junction = 30 min
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