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

The train ran at less than its full speed, which means it ran at a fraction of its full speed. That fraction is 5/12, which translates into a decimal of 0.416 These facts mean that at full speed the train would have reached its destination in less than 18 hours.
Let t = time at full speed
then t = 0.416 x 18hrs
then t = 7.488hrs
time saved = 18 hrs - 7.488 hrs = 10.5 hrs

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

Distance = 300 m

∴ Time taken to cover this distance = 30015

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.

(6-4)x=240 ==> x=120 seconds
why 240 is, since they had to meet for the first time

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