Two persons start running simultaneously around a circular track of length 300 m from the same point at speeds of 15 km/hr and 25 km/hr. When will they meet for the first time any where on the track if they are moving in opposite directions ?

Correct Answer: None of these

Explanation:

Let t be the time after Kajol starts, when she meets Ajay, then 

               t = 300/(x+y) 

 This should be less than 2.5 or (x+y)>120 

Since       y= 3x/2  =>  y > 72

This (y>72) is greater than 67.5 km/h and hence Shahrukh will always overtake Ajay before he meets Kajol.

Correct Answer: 48 kmph

Explanation:

Let the initial speed of Akhil be '4p' kmph

Then speed after decrease in speed = '3p' kmph

We know that, 

Change in speed == Change in time

According to the given data,

$$\begin{gathered} 24 3 p - 24 4 p = 35 - 25 60 \\ = > p = 12 \end{gathered}$$

 

Hence, the initial speed of Akhil = 4p = 4 x 12 = 48 kmph.

Correct Answer: 1400

Explanation:

Given the ratio of the circumference of front wheel  is 40 inches and back wheel is 70 inches. 

 

Distance covered = Circumference of the wheel × No. of Revolutions made by the wheel

 

If n is the number of revolutions made by back wheel, the number of revolutions made by front wheel is n+15

 

Distance covered by both the wheels is the same

 

i.e, 40*(n+15)=70n

 

 n=20 

 

 

 

                Front wheel      :      Back Wheel 

 

 Circumference       40      :      70 

 

 Revolutions           35      :      20

 

 

 

Distance covered  :  40×35 = 70×20 = 1400 inches.

Correct Answer: 70 kms

Explanation:

Let the time taken by train be 't' hrs.

Then,

40 t = 35 t + 15 60

40t = 35t + 35/4

t = 7/4 hrs

Therefore, Required length of the total journey d = s x t

= 40 x 7/4

= 70 kms.

Correct Answer: 4.18

Explanation:

Distance to be covered =  ?D = 40 ? km 

Relative speed of bikers = 16 + 14 = 30 kmph.

 

Now,  t i m e = d i s tan c e s p e e d =   40 ? 30 = 4.18 hrs.

Correct Answer: 99

Explanation:

Let, Distance between A and B = d

 

Distance travelled by P while it meets Q = d + 11

 

Distance travelled by Q while it meets P = d ? 11

 

Distance travelled by Q while it meets R = d + 9

 

Distance travelled by R while it meets Q = d ? 9

 

Here the ratio of speeds of P & Q => SP : SQ = d + 11 : d ? 11

 

The ratio of speeds of Q & R => SQ : SR = d + 9 : d ? 9

 

But given Ratio of speeds of P & R => P : R = 3 : 2

  S P S R = S P S Q x S Q S R = d + 11 d + 9 d - 11 d - 9

 

=>  d + 11 d + 9 d - 11 d - 9 = 3/2

 

=>  d = 1, 99

 

=> d = 99 satisfies.

 

Therefore, Distance between A and B = 99

Correct Answer: 17 hours

Explanation:

In this type of questions we need to get the relative speed between them,
The relative speed of the boys = 5.5kmph ? 5kmph
= 0.5 kmph

Distance between them is 8.5 km
Time = Distance/Speed
Time= 8.5km / 0.5 kmph = 17 hrs

Correct Answer: bm/60c

Explanation:

Substitute sensible numbers and work out the problem. Then change the numbers back to letters. For example if the machine puts 6 caps on bottles in 2 minutes, it will put 6 /2 caps on per minute, or (6 /2) x 60 caps per hour. Putting letters back this is 60c/m.If you divide the required number of caps (b) by the caps per hour you will get time taken in hours. This gives bm/60c

Correct Answer: 6 mile/hr

Explanation:

Let the speed of river and boat be 'r' m/min and 'b' m/min.
so relative speed in upstream (b-r)m/min and in downstream (b+r)m/min.
Now in upstream distnce covered in 5 min is 5(b-r)miles
so total distnce covered => 1 + 5(b-r)miles in upstream
In downstream distance covered in 5min is 5(b+r)miles
Now 1 + 5(b-r) = 5(b+r)
1+5b-5r = 5b+5r
1 = 10r
r = 1/10 mile/min => 6 mile/hr.

Correct Answer: 330/29 m/s

Explanation:

Second gun shot take 30 sec to reach rahul imples distance between two.

given speed of sound = 330 m/s

Now, distance = 330 m/s x 30 sec 

 

Hence, speed of the bus = d/t = 330x30/(14x60 + 30) = 330/29 m/s.