LATEST

    LDC EXAM PREPARATION    ||         SI / BDO EXAM PREPARATION 2020    ||        PREVIOUS QUESTIONS 2020 DEGREE LEVEL     ||        PREVIOUS QUESTIONS LDC     PSC EXAM PROGRAMME 2020     ||        TODAY'S EXAM RESULTS 2020    ||        FINAL ANSWER KEY    ||    FREE STUDY MATERIALS (LDC)     ||    FREE STUDY MATERIALS (DEGREE LEVEL)     ||    CURRENT AFFAIRS-MALAYALAM 2020     ||    CURRENT AFFAIRS-ENGLISH 2020

Monday, 29 April 2019

MATHS (SOLVED IN STEPS) PROBLEMS ON TRAINS - 04

22. A 300 metre long train crosses a platform in 39 seconds while it crosses a post in 18 seconds. What is the length of the platform?
A. 150 m                     B. 350 m                 C. 420 m                D. 600 m
Answer : Option B
Explanation :
Length of the train
= distance covered in crossing the post
= speed × time
= speed × 18
ie,300= speed × 18
Speed of the train = 300/18 m/s = 50/3 m/s
Time taken to cross the platform = 39 s
(300+x)/(50/3) = 39 s where x is the length of the platform
300+x = (39 × 50) / 3 = 650 meter
x = 650-300 = 350 meter


23. A train crosses a post in 15 seconds and a platform 100 m long in 25 seconds. Its length is
A. 150 m                    B. 300 m                  C. 400 m                     D. 180 m
Answer : Option A
Explanation :
Assume x is the length of the train and v is the speed x/v = 15
=> v = x/15
(x+100)/v = 25
=> v = (x+100)/25
Ie, x/15 = (x+100)/25
=> 5x = 3x+ 300
=> x = 300/2 = 150

24. A train , 800 meter long is running with a speed of 78 km/hr. It crosses a tunnel in 1 minute. What is the length of the tunnel (in meters)?
A. 440 m                     B. 500 m                    C. 260 m                  D. 430 m
Answer : Option B
Explanation :
Distance = 800+x meter where x is the length of the tunnel
Time = 1 minute = 60 seconds
Speed = 78 km/hr = 78×10/36 m/s = 130/6 = 65/3 m/s
Distance/time = speed
(800+x)/60 = 65/3
=> 800+x = 20×65 = 1300
=> x = 1300 - 800 = 500 meter


25. Two train each 500 m long, are running in opposite directions on parallel tracks. If their speeds are 45 km/ hr and 30 km/hr respectively, the time taken by the slower train to pass the driver of the faster one is
A. 50 sec                  B. 58 sec               C. 24 sec                D. 22 sec
Answer : Option C
Explanation :
Relative speed = 45+30 = 75 km/hr = 750/36 m/s = 125/6 m/s
We are calculating the time taken by the slower train to pass the driver of the faster one
Hence the distance = length of the smaller train = 500 m
Time = distance/speed = 500/(125/6) = 24 s

26. Two trains are running in opposite directions in the same speed. The length of each train is 120 meter. If they cross each other in 12 seconds, the speed of each train (in km/hr) is
A. 42                   B. 36                     C. 28                    D. 20
Answer : Option B
Explanation :
Distance covered = 120+120 = 240 m
Time = 12 s
Let the speed of each train = v. Then relative speed = v+v = 2v
2v = distance/time = 240/12 = 20 m/s
Speed of each train = v = 20/2 = 10 m/s
= 10×36/10 km/hr = 36 km/hr

27. A train 108 m long is moving at a speed of 50 km/hr . It crosses a train 112 m long coming from opposite direction in 6 seconds. What is the speed of the second train?
A. 82 kmph                  B. 76 kmph                  C. 44 kmph               D. 58 kmph
Answer : Option A
Explanation :
Total distance = 108+112 = 220 m
Time = 6s
Relative speed = distance/time = 220/6 m/s = 110/3 m/s
= (110/3) × (18/5) km/hr = 132 km/hr
=> 50 + speed of second train = 132 km/hr
=> Speed of second train = 132-50 = 82 km/hr


28. How many seconds will a 500 meter long train moving with a speed of 63 km/hr, take to cross a man walking with a speed of 3 km/hr in the direction of the train ?
A. 42                          B. 50                            C. 30                    D. 28
Answer : Option C
Explanation :
Distance = 500m
Speed = 63 -3 km/hr = 60 km/hr = 600/36 m/s =
50/3 m/s
Time taken = distance/speed= 500/(50/3) = 30 s
* MATHS (SOLVED IN STEPS ==> Ratio and Proportion
* MATHS (SOLVED IN STEPS ==> Progressions
* MATHS (SOLVED IN STEPS ==> Percentage
* MATHS (SOLVED IN STEPS ==> Surds and Indices
* MATHS (SOLVED IN STEPS ==> Calendar
* MATHS (SOLVED IN STEPS ==> Square and cube
* MATHS (SOLVED IN STEPS ==> Simplification
* MATHS (SOLVED IN STEPS ==> Problems on Average
* MATHS (SOLVED IN STEPS ==> HCF & LCM 
* MATHS (SOLVED IN STEPS ==> Profit and Loss
* MATHS (SOLVED IN STEPS ==> Problems on Age 
* MATHS (SOLVED IN STEPS ==> Pipe and Cisterns
* MATHS (SOLVED IN STEPS ==> ODD MAN
* MATHS (SOLVED IN STEPS ==> TIME & WORK



Related Links
* SCERT KERALA TEXT BOOKS FOR CLASS II, IV, VI, VIII, IX, X, XII – FREE DOWNLOAD ---> Click here
* NCERT & CBSE TEXT BOOKS FOR ALL CLASSES – FREE DOWNLOAD ---> Click here
* NCERT & CBSE TEXT BOOKS SOLUTIONS FOR ALL CLASSES ---> Click here
Loading...

No comments:

Post a comment