Skip to main content

Two trains of equal lengths take 10 seconds and 15 seconds r


Two trains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. If the length of each train be 120 metres, in what time (in seconds) will they cross each other travelling in opposite direction?

A.10B.12
C.15D.20



Answer: Option B
Explanation:
Speed of the first train =(120(m/sec = 12 m/sec.
10
Speed of the second train =(120(m/sec = 8 m/sec.
15
Relative speed = (12 + 8) = 20 m/sec.
Therefore Required time =[(120 + 120)]sec = 12 sec.
20

Comments

Post a Comment

Popular posts from this blog

Find the number of perfect squares in the given series 2013, 2020, 2027,.

Find the number of perfect squares in the given series 2013, 2020, 2027,................, 2300   (Hint 44^2=1936) a. 1   b. 2    c. 3   d. Can’t be determined Answer: a Explanation: The given series is an AP with common difference of 7. So the terms in the above series are in the form of 2013 + 7k.  We have to find the perfect squares in this format in the given series. Given that 44^2 = 1936. Shortcut: To find the next perfect square, add 45th odd number to 44^2. So 45^2 = 1936 + (2 x 45 -1) = 2025 46^2 = 2025 + (2 x 46 - 1) = 2116 47^2 = 2116 + (2 x 47 - 1) = 2209 Now subtract 2013 from the above numbers and divide by 7. Only 2209 is in the format of 2013 + 7k.  One number satisfies.
Post a Comment
Read more