The distance between two cities M and N is 330km. A train starts from M at 8 AM. and travels towards N at 60 km/hr. Another train starts from N at 9 AM. and travels towards M at 75 km/hr. At what time do they meet?
Distance travelled by first train in one hour
= 60 x 1 = 60 km
Therefore, distance between two train at 9 AM.
= 330 – 60 = 270 km
Now, Relative speed of two trains = 60 + 75 = 135 km/hr
Time of meeting of two trains =270/135=2 hrs.
Therefore, both the trains will meet at 9 + 2 = 11 AM
The driver of a BUS sees a van 60m ahead of him. After 30seconds the van is 60m behind. If the speed of the BUS is 45kmph, what is the speed of the Van?
Relative speed = (60+60)/30 = 4m/s = 4 * 18/5 = 14.4kmph
Speed of the van = 45 – 14.4= 30.6kmph
Two TRUCKS of equal lengths take 10 seconds and 15 seconds respectively to cross a LAMP post. If the length of each TRUCK be 300 metres, in what time will they cross each other travelling in opposite direction?
Speed of the first TRUCK = [300/10] m/sec = 30 m/sec.
Speed of the second TRUCK = [300/15] m/sec =20 m/sec.
speed = (30 + 20) m/sec = 50m/sec.
Required time = (300+300)/50secc = 12 sec
RAM takes 4hrs 30min in walking to a certain place and riding back. He would have gained 2hrs by riding both ways. The time he would take to walk both ways, is:
Two friends RAHIM and PIHU are travelling from point A to B, which are 600km apart. Travelling at a certain speed RAHIM takes 1hr more than PIHU to reach point B. If RAHIM doubles his speed he will take 1hr 30mins less than PIHU to reach point B. At what speed was RAHIM driving from point A to B?
T = D/S. Let x be the speed
600/x = T+1 , 600/2x = T – 3/2
(600-x)/x = (600+3x)/2x
1200-12x = 600+3x ==>x=120km
A TRAIN starts at 40km/hr and it increases its speed in every 1 hour by 2km/hr. Then the maximum distance covered by him in 24 hrs is
Speed of the train : 40km/hr
it increases its speed in every 1 hr by 2km/hr.
Distance covered by every 1 hr will be 40,42,44….upto 12terms. i.e. (for 24hrs)
Sum of 1st n terms=n/2 ( (2a+(n-1)d)
12/2 * (2*40+11*2)==>12/2 * (80+22)==>612km
If a BUS runs at 45km/hr, it reaches its destination late by 10 mins but if runs at 60km/hr it is late by 4min. What is the correct time for the journey?
Distance = diff in time *(S1*S2)/S1-S2
D=[10-4]/60hr * (45*60)/[60-45] = 6/60 * 45*60/15 ==>18km
time T=D/S(take any one of the speed) 18/45 =2/5hrs = 2/5*60=24min
then correct time is 24-10=14mins
Two BUSES starts at the same time from MATHURA and RACHI and proceed towards each other at the rate of 40km/hr and 37 1/2km/hr. When they meet it is found that one BUS has traveled 200km more than the other BUS. What is the distance between MATHURA and RACHI?
Speed ratio 40:37 1/2==>40: 75/2==>80:75 ie 16:15
ratio diff betwwen speed is 1[16-15]
1 ===> 200 (more distance)
Two cars start at same time from KOLKATA and Mangalore, which are 250km apart. If the two cars travel towards each other, they meet after 1hr and if they travel in same direction they meet after 5hrs. What is the speed of the car starts from KOLKATA if it is know that the one which started from KOLKATA has more speed than the other one?
Here we have two speeds. We get 2 equations as.
250/1hr = K+M—-1
250/5hr = K-M—-2
solving 2 eqn K=150km/hr.
Car M leaves the city at 5pm and is driven at a speed of 30km/hr. 3hrs later another car N leaves the city in the same direction as car M. In how much time will car N be 12kms ahead of car M if the speed of car N is 50km/hr?
Car M travels 3hrs. 3*30=90km
Difference between speeds 50-30=20km/hr
Distance ahead 12km . 90+12=102km