Tricks to solve Speed Time and Distance Problems for Competitive Exams

TIME,DISTANCE AND SPEED

Distance covered per unit time is called SPEED

i,e., speed=distance/time

the above equation can be rearranged as

time=distance/speed

distance=speed*time

1.km/hr to m/sec conversion

zkm/hr = z x 5/18 m/sec

2.m/sec to km/hr conversion

z m/sec = z x 18/5 km/hr
3.If the ratio of the speeds of A and B is a : b, then the ratio of the
the times taken by then to cover the same distance is
1/a
:
1/b
or b:a
4.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
km/hr.
x + y

 

WORKSAMPLES:

1. A person crosses a 600 m long street in 5 minutes. What is his speed in km per hour?
A. 3.6
B. 7.2
C. 8.4
D. 10

SOLUTION WITH 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

2.If a person walks at 14 km/hr instead of 10 km/hr, he would have walked 20 km more. The actual distance travelled by him is:
A. 50 km
B. 56 km
C. 70 km
D. 80 km

SOLUTION WITH EXPLANATION:

Let the actual distance travelled be x km.

Then, x = x + 20
10 14

 14x = 10x + 200

 4x = 200

x = 50 km.

 

1.A person crosses a 600 m long street in 5 minutes. What is his speed in km per hour?

2.If a person walks at 14 km/hr instead of 10 km/hr, he would have walked 20 km more. The actual distance travelled by him is?

3.Excluding stoppages, the speed of a bus is 54 kmph and including stoppages, it is 45 kmph. For how many minutes does the bus stop per hour?

4. A man complete a journey in 10 hours. He travels first half of the journey at the rate of 21 km/hr and second half at the rate of 24 km/hr. Find the total journey in km?

5.A man on tour travels first 160 km at 64 km/hr and the next 160 km at 80 km/hr. The average speed for the first 320 km of the tour is?

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