A) 2:1 | B) 3:2 |

C) 4:3 | D) 5:4 |

Explanation:

Note : If two trains (or bodies) start at the same time from points A and B towards each other and after crossing they take a and b sec in reaching B and A respectively, then: (A's speed) : (B's speed) = (b : a)

Therefore, Ratio of the speeds of two trains = = 3 : 2

A) 250 mts | B) 400 mts |

C) 320 mts | D) 390 mts |

Explanation:

Let the length of the 1st train = L mts

Speed of 1st train = 48 kmph

Now the length of the 2nd train = L/2 mts

Speed of 2nd train = 42 kmph

Let the length of the bridge = D mts

Distance = L + L/2 = 3L/2

Relative speed = 48 + 42 = 90 kmph = 90 x 5/18 = 25 m/s(opposite)

Time = 12 sec

=> 3L/2x25 = 12

=> L = 200 mts

Now it covers the bridge in 45 sec

=> distance = D + 200

Time = 45 sec

Speed = 48 x5/18 = 40/3 m/s

=> D + 200/(40/3) = 45

=> D = 600 - 200 = 400 mts

Hence, the length of the bridge = **400** mts.

A) 36 kmph | B) 30 kmph |

C) 34 kmph | D) 40 kmph |

Explanation:

Let the speed of the faster train be 'S' kmph

Then speed of the slower train will be '(S-5)' kmph

Time taken by faster train = 350/S hrs

Time taken by slower train = 350/(S-5) hrs

=> S = 30 km/hr.

A) 180 mts | B) 190 mts |

C) 200 mts | D) 210 mts |

Explanation:

Let the length of the train be 'L' mts

let the speed of the train be 'S' m/s

Given it crosses a pole in 10 sec=> L/S = 10 ......(1)

Given it takes 20 sec (double of pole) to cross a platform of length 200 mts

=> (L + 200)/S = 20

=> L/S + 200/S = 20

But from (1) L/S = 10

=> 200/S = 20 - 10

=> S = 20 m/s

Then, from (1)

=> L = 10 x 20 = 200 mts.

Hence, the length of the train = 200 mts.

A) 7.71 sec | B) 10.48 sec |

C) 9.36 sec | D) 8.45 sec |

Explanation:

Given L1 = 140 m

L2 = 160 m

S1 = 60 km/hr

S2 = 80 km/hr

From the question we get,

S1 + S2 = (L1 + L2) / T

=> (60 + 80) 5/18 m/s = 140 + 160/T

=> T = 54/7 = 7.71 sec

A) 6.24 sec | B) 6.58 sec |

C) 7.325 sec | D) 7.65 sec |

Explanation:

Here total distance = 154 + 101 = 255 mts

Given speed = 120 kmph = 120x5/18 m/sec

Hence, Time = d/s = 255x18/120x5 = 7.65 sec