Quiz 1

as we know the speed of student is decreased by 25%  so,
Speed left = (overall speed -decreased speed)/(overallspeed) speed left = 75/100 =3/4.
speed is inversely proportional to time it means, S =1/T then
3/4s =4/3t
so,  from above question
4t/3-t = 8/60
t=2/5
t= 2/5*60 = 24 Minutes
hence answer is 24 minutes

Explanation: Here, speed= Distance/ Time​

As per question,
Here s = Speed
The train is running at 5/12​ of its own speed and reaches the place in 18 hrs.

d= (5/12​)*18s

⇒d=7.5s ………..(1)

Let t be the time taken by the train to reach the place with its actual speed.

d=st ………..(2)

from (1) and (2), we get

7.5s = st

⇒t= 7.5 hours

Time that could be saved = 18 - 7.5
= 10.5 hrs.

According to question, relative speed = (8 + 7) = 15 m/s

Distance = 300 m

∴ Time taken to cover this distance = 300/15

Let the speed of the slower train be x m/sec.
Then, speed of the faster train = 2x m/sec.
Relative speed = (x + 2x) m/sec = 3x m/sec.
==> (120 + 120)/12 = 3x
==> x=20/3
==>So, speed of the faster train =40/3m/sec
==> (40/3)*(18/5)
==> 48 km/hr.

distance is same let the speed is x
then x*7=(x+12)*5
2x=60
x=30km/hr
so the distance b/w two point=30*7= 210km

Correct Answer is Option [B]
Let the speed be \"x\" & usual time taken be \"t\".
Therefore, speed = (distance/time) => x=(d/t)
By decreasing by 25%, 0.75x=(d/t+8)
Since the distance is same, xt = 0.75x * (t+8) => t=24 min.
New time of reaching the office is t+8 = 24+8 = 32mins.

Relative Speed = 4 m/s + 6 m/s = 10 m/s

Distance = 240

Time taken to cover this distance = 240/10
= 24 s

 

Speed of the bus without stoppage=64 km/hr
Speed of the bus with stoppage=48km/hr
Difference in speed=16 km/hr
so,the time taken in the stoppages = time taken to cover 16 km=(16/64)hr = 1/4 hr =15 min

First cart speed will be 24/3=8
Second cart speed is 120/2=60
So, ratio is 8/60=2/15

Let the normal speed be x km/hr, then
Difference between the time taken to cover 300 km at the rate of \\\\\\\\\\\\\\\'x\\\\\\\\\\\\\\\' and \\\\\\\\\\\\\\\'x+5\\\\\\\\\\\\\\\' is 2 hours
So, [(300/x) - 300/(x+5)]=2
=> (300x+1500-300x)/x(x+5) =2
=> x^2+ 5x -750=0
=> (x-25)(x+30)=0
=> x=25