Aptitude - Time and Distance - Discussion

Discussion Forum : Time and Distance - General Questions (Q.No. 1)
1.
A person crosses a 600 m long street in 5 minutes. What is his speed in km per hour?
3.6
7.2
8.4
10
Answer: Option
Explanation:

Speed = 600 m/sec.
5 x 60

   = 2 m/sec.

Converting m/sec to km/hr (see important formulas section)

   = 2 x 18 km/hr
5

   = 7.2 km/hr.

Discussion:
186 comments Page 1 of 19.

Stevie Dee said:   7 years ago
Hey, guys, The sum is relatively easy if you know how and while there are some good examples above, it can be broken down even further in the order you can understand it better, especially when it comes to 18/5 part of the formula. So let's break it down (sorry for the long explanation and simple steps).

PART 1

1. Divide the Distance by the time: 600m / 5min = 120m/min.
2. Divide the new Distance (120m/min) by 60 (the number of seconds in a minute) to give you the distance travelled per second: 120m/min / 60 = 2m/sec.

PART 2

We have established that we are travelling at 2m/sec (write that down and leave it for now, we will come back to this later). Now we need to breakdown 1Km into meters (1000m) and 1hour into seconds in order to change from meters per second to Kilometres per hour.

1. 1 Kilometre in length is 1000m (simple)
2. Next work out how many seconds are in 1 hour of time. There are 60min in an hour and 60 seconds in each minute, therefore to get the total seconds we must Multiply 60min with 60 Seconds: 60min x 60Sec = 3600Sec in 1hr of time.
3. This now leaves us with 3600/1000. At this point we can complete the question and there is no real need to break it down further, please follow the example: 2m/sec x 3600sec / 1000m = 7.2Kph

4, However, for those of you still wondering where they got 18/5 from, the above numbers can be broken down further to make it easier to work with if you are not using with a calculator etc. if you were to remove the zeros from 3600/1000 you are left with 36/10 and if you were to half these numbers again you will come to 18/5 (and so on). You can apply both these number to the same sum and the results will be the same, you have just made it easier to calculate:

Answer 1:
600 / 5 = 120 / 60 = 2m/sec
1km = 1000m
1hr: 60 x 60 = 3600sec
2 x 3600 / 1000 =7.2

Answer 2:
600 / 5 = 120 / 60 = 2m/sec
1km = 1000m
1hr: 60 x 60 = 3600sec
36/10
2 x 36/10 = 7.2

Answer 3:
600 / 5 = 120 / 60 = 2m/sec
1km = 1000m
1hr: 60 x 60 = 3600sec
36/10
18/5
2 x 18/5 =7.2

I hope this helped?

Sundar said:   1 decade ago
Hi Vidu and Sushree,

You questions is from where did 60 come?

Please concentrate on the unit name mentioned along with the numbers.

Speed = Distance/Time

Here Distance = 600 meters and Time = 5 mins.

Therefore, Speed = 600/5 meters/minutes.

We have to write it as in terms of meters/seconds. So we are multiplying it with 60 (1 min = 60 seconds).

So, Speed = 600/(5 x 60 sec) meters/seconds.

I strongly suggest all newbies to go through the basic formulas before posting your doubts here. So, kindly go through the basic formulas for solving Time and Distance problems.

Have a nice day!

Prabakaran said:   6 years ago
The speed formula= distance/time.

So we have speed=600 metres/ 5 min
In this 5 is a minute value so we have to convert it into seconds
Because metres/seconds is a current formula
so we need to change the 5 min value into seconds
1 min= 60 seconds.
So 5 min = 5*60.
= 300 sec that's why 60 will come in this section
now we calculate speed = 600/300 m/sec.
= 2 m/sec

On step 2:
we need the man speed in km/hour.
so we need to convert m/sec into km/hour.
using 1000/3600= 5/18.
Because 1 km= 1000 m.
and 1 hour= 3600 sec ( 1min= 60 sec then 1hour= 60 min so 60*60= 3600 sec)
the answer is 2*5/18= 7.2 km/hour.

Deepa.pk said:   1 decade ago
@jayan,jashwa
to convert km/hr to m/sec, we hav to do in dis way.....
1km=1000m
1hr=3600sec
1km/hr=1000/3600 m/sec
therefore 1km/hr=5/18 m/sec


similarly to convert m/sec, we hav to in reverse way.....
1000m=1km ---> m=1/1000km
3600sec=1hr ---> sec=1/3600hr
its just a normal cross multiplication
m/sec=3600/1000 km/hr
therefore m/sec=18/5 km/hr

its not necessary to do al these steps. i included al the steps just for your better understanding......... hope u can understand now

thank u

Nvll said:   10 years ago
@Vinoth.

It doesn't actually matter he will be vaporized in a few ms so will never hear it.

I don't no one person who talks about m/second so why the need to convert to m/s anyway.

I came on to this site to find out what a wind speed of 2 m/s is, who talks about a wind speed of 2 m/s? 7.2 km/hr or 4 m/h or 3.8 knots I can work out, but 2m/s? Very geeky.

Umang Joshi said:   3 years ago
Speed = distance*time guys now,
Speed = 5min OR 5*60= 300 second
Distance = 600m.

By using above formula;
s = D/T.
S = 600/5 * 60.
= 2m/sec.

Converting it into km/h to m/sec we do 5/18 which is 1000/3600,
For converting m/s into km/hour use 18/5 -----> (1)
Now using (1).

18/5*2 = 7.2 km/hour answer which is option (B)
hope you all got it.

Priya said:   3 years ago
We know that speed= distance/time.

But we can't find the speed for m/min.
So, we can first convert 5 mins to sec. 5*60 = 300 s.
Now we need to find the speed= distance/time= 600/300= 2 m/s.

But we need km/hour. so for converting m/s to km/hour we need to multiply the speed(in m/s) * 18/5 (5/18 for km/hour into m/s).
So, 2*18/5=36/5= 7.2.

Manu said:   7 years ago
Step1: We are finding speed = distance/time.
Distance= 600mts,
Time = 5minutes, we are converting time is minutes into seconds so,
t = 5 * 60 = 300
Then, s =d/t=600/300= 2 mt per sec is comminng.
Now we r converting mt per sec to km per hour.
Then formula is x * 18/5,here x is s ,now 2*18/5=36/5=7.2km/hr .
Now speed =7.2km/hr.

Ganesh said:   1 decade ago
To convert km/hr to m/sec, we hav to do in dis way.....
1km=1000m
1hr=3600sec
1km/hr=1000/3600 m/sec
therefore 1km/hr=5/18 m/sec


Similarly to convert m/sec, we hav to in reverse way.....
1000m=1km ---> m=1/1000km
3600sec=1hr ---> sec=1/3600hr
its just a normal cross multiplication
m/sec=3600/1000 km/hr
therefore m/sec=18/5 km/hr

Anmol said:   7 years ago
Hi everyone,

Speed = Distance/Speed
Time= Distance/Speed
Distance=Speed x Time

1km=1000m,and 1hr=3600seconds
Therefore, 1km/hr=1000m/3600sec =5m/18sec=5/18m/s.

Therefore,
to change a speed in km/hr to a speed in m/sec, multiply by5/18.
Conversely, to change a speed in m/sec to a speed in km/hr, multiply by 18/5.


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