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**Important Formulas :**

i) Speed = Distance/Time

ii) Time = Distance/speed

iii) Distance = speed*time

iv) 1km/hr = 5/18 m/s

v) 1 m/s = 18/5 Km/hr

vi) If the ratio of the speed of A and B is a:b,then the ratio of the time taken by them to cover the same distance is 1/a : 1/b or b:a

vii) suppose a man covers a distance at x kmph and an equal distance at y kmph.then the average speed during the whole journey is (2xy/x+y) kmph

viii) An object that moves at a constant rate is said to be in uniform motion. The formula d = rt gives the relationship between distance d, rate r, and time t. Uniform motion problems may involve objects going the same direction, opposite directions, or round trips.

Questions :

1.) Walking at the rate of 4kmph a man cover certain distance in 2hr 45 min. Running at a

speed of 16.5 kmph the man will cover the same distance in.

A. 12 min B. 25 min C. 40min D. 60 min**Answer**: Option C**Explanation**: Distance = Speed * time

4*11/4 = 11km

New Speed = 16.5 kmph

Therefore time = D/S = 11/16.5 = 40min

2.) A train covers a distance in 50 min, if it runs at a speed of 48kmph on an average. The

speed at which the train must run to reduce the time of journey to 40min will be.

A. 45 min B. 60 min C. 75 min D. None of these**Answer**: Option B

E**xplanation**: Time = 50/60 hr = 5/6hr

Speed = 48mph

distance = S*T = 48 * 5/6 = 40km

time = 40/60hr = 2/3hr

New speed = 40* 3/2 kmph = 60kmph

3.) Two boys starting from the same place walk at a rate of 5kmph and 5.5kmph

respectively. What time will they take to be 8.5km apart, if they walk in the same

direction?

A. 17 hrs B. 25 hrs C. 31 hrs D. 45 hrs**Answer**: Option A**Explanation:**

The relative speed of the boys = 5.5kmph – 5kmph

= 0.5 kmph

Distance between them is 8.5 km

Time= 8.5km / 0.5 kmph = 17 hrs

4.) 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?

A. 4 B. 6 C. 8 D. None of these**Answer**: Option D**Explanation:**

Due to stoppages, it covers 9 km less.

Time taken to cover 9 km = (9/54 x 60) min = 10 min.

5.) 2 trains starting at the same time from 2 stations 200km apart and going in opposite

direction cross each other at a distance of 110km from one of the stations. What is the

ratio of their speeds?

A. 7:3 B. 11:9 C. 18:4 D. None of these**Answer**: Option B**Explanation:**

In same time, they cover 110km & 90 km respectively

so ratio of their speed =110: 90 = 11: 9

6.) In covering a distance of 30 km, Sachin takes 2 hours more than Rohit. If Sachin

doubles his speed, then he would take 1 hour less than Rohit. Sachin speed is:

A. 5 kmph B. 16 kmph C. 21 kmph D. None of these**Answer:** Option A**Explanation:**

Let Sachin’s speed be X km/hr.

Then, 30/x - 30/2x = 3

6x = 30

x = 5 km/hr.

7.) A train 140m long running at 60kmph. In how much time will it pass a platform 260m

long?

A. 5 kmph B. 16 kmph C. 21 kmph D. None of these**Answer**: Option A**Explanation:**

Distance travelled = 140 + 260m = 400m,

Speed = 60 * 5/8 = 50/3m

Time = 400 * 3/50 = 24 Seconds

8.) The ratio between the speeds of two trains is 7: 8. If the second train runs 440 kms in 4

hours, then the speed of the first train is:

A. 47.4 km/hr B. 57.19 km/hr C. 68.13 km/hr D. None of these**Answer:** Option D**Explanation:**Let the speed of two trains be 7x and 8x km/hr.

Then, 8x = (440/4) = 110

x = (110/8) = 13.75

Speed of first train = (7 x 13.75) km/hr = 96.25 km/hr.

9.) Sachin can cover a distance in 1hr 24min by covering 2/3 of the distance at 4 kmph

and the rest at 5kmph.the total distance is?

A. 5km B. 6km C. 7km D. 8km**Answer:** Option D**Explanation**:

Distance = 2/3S

distance=1-2/3S=1/3S

21/15 hr=2/3 S/4 + 1/3s /5

84=14/3S * 3

S= 6km

10.) A person walks at 5kmph for 6hr and at 4kmph for 12hr.The average speed is.

A. 4 1/3 B. 7 2/3 C. 9 ½ km D. 8km**Answer:** Option D**Explanation:**

Avg speed = total distance/total time

= 5*6 + 4*12 / 18

=4 1/3 mph

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very good....sure some such type question will come in exam.......

ReplyDeletethanx a lot

ReplyDeletegood ....more questions of DI

ReplyDelete