IIT JEE Practice Question and Answer

Q: fifteen persons are sitting around a circular table facing the centre. What is the probability that three particular persons sit together ? 3645 0

  • 1
    3/91
    Correct
    Wrong
  • 2
    2/73
    Correct
    Wrong
  • 3
    1/91
    Correct
    Wrong
  • 4
    3/73
    Correct
    Wrong
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Answer : 1. "3/91"
Explanation :

Answer: A) 3/91 Explanation: In a circle of n different persons, the total number of arrangements possible = (n - 1)!Total number of arrangements = n(S) = (15 – 1)! = 14 !Taking three persons as a unit, total persons = 13 (in 4 units)Therefore no. of ways for these 13 persons to around the circular table = (13 - 1)! = 12!In any given unit, 3 particular person can sit in 3!. Hence total number of ways that any three person can sit =n(E) = 12! X 3!Therefore P (E) = probability of three persons sitting together = n(E) / n(S) = 12! X 3 ! / 14!= 12!x3x2 / 14x13x12! = 6/14x13 = 3/91

Q: If 34 men completed 2/5th of a work in 8 days working 9 hours a day. How many more man should be engaged to finish the rest of the work in 6 days working 9 hours a day ? 3644 0

  • 1
    101 men
    Correct
    Wrong
  • 2
    112 men
    Correct
    Wrong
  • 3
    102 men
    Correct
    Wrong
  • 4
    120 men
    Correct
    Wrong
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Answer : 3. "102 men"
Explanation :

Answer: C) 102 men Explanation: From the above formula i.e (m1 x t1/w1) = (m2 x t2/w2) so, [(34 x 8 x 9)/(2/5)] = [(M x 6 x 9)/(3/5)] so, M = 136 men   Number of men to be added to finish the work = 136-34 = 102 men.

Q: A periscope works by the principle of 3641 0

  • 1
    Total internal reflection
    Correct
    Wrong
  • 2
    Refraction
    Correct
    Wrong
  • 3
    Diffraction
    Correct
    Wrong
  • 4
    Reflection & Refraction
    Correct
    Wrong
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Answer : 1. "Total internal reflection"
Explanation :

Answer: A) Total internal reflection Explanation: A periscope is an optical instrument that uses a system of prisms, lenses, or mirrors to reflect images through a tube.       Light from a distant object strikes the top mirror and is then reflected at an angle of 90 degrees down the periscope tube. At the bottom of the periscope, the light strikes another mirror and is then reflected into the viewer’s eye.   Hence, A periscope works by the principle of Total internal reflection.

Q: In what way does ocean water move globally? 3641 0

  • 1
    Along cold water currents from the equator to the poles.
    Correct
    Wrong
  • 2
    Along warm water currents from the warmer regions to colder regions
    Correct
    Wrong
  • 3
    Along warm water currents from the equator to the poles
    Correct
    Wrong
  • 4
    None of the above
    Correct
    Wrong
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Answer : 3. "Along warm water currents from the equator to the poles"
Explanation :

Answer: C) Along warm water currents from the equator to the poles Explanation:

Q: The 1911 Chinese revolution ended the rule of the 3636 0

  • 1
    Ming dynasty
    Correct
    Wrong
  • 2
    Mongolians dynasty
    Correct
    Wrong
  • 3
    Song dynasty
    Correct
    Wrong
  • 4
    Manchus dynasty
    Correct
    Wrong
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Answer : 4. "Manchus dynasty"
Explanation :

Answer: D) Manchus dynasty Explanation: It was the Qing Dynasty, who was a Manchu Dynasty whose rule ended in 1911 Chinese revolution.

Q: Simplify the following equation 55.55 + 155 + 15.55 + 0.5 + 0.05 = ? 3635 0

  • 1
    226.65
    Correct
    Wrong
  • 2
    196.55
    Correct
    Wrong
  • 3
    202.35
    Correct
    Wrong
  • 4
    216.66
    Correct
    Wrong
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Answer : 1. "226.65"
Explanation :

Answer: A) 226.65 Explanation: 55.55 + 155 + 15.55 + 0.5 + 0.05 = ?    55.55 155.00  15.55    0.5    0.05 _______ 226.65 _______   Hence, the value of the given equation 55.55 + 155 + 15.55 + 0.5 + 0.05 = 226.65.

Q: In a certain code ARCHIVE is written as DSBGFWJ. How is SYSTEMS is written in that code ? 3633 0

  • 1
    TZTSTUN
    Correct
    Wrong
  • 2
    TZTSTNF
    Correct
    Wrong
  • 3
    TZTUTNF
    Correct
    Wrong
  • 4
    TZTNTFS
    Correct
    Wrong
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Answer : 2. "TZTSTNF"
Explanation :

Answer: B) TZTSTNF Explanation: ARC -> CRA ->(+1) DSB    H ->     H ->(-1) GIVE  ->  EVI ->(+1) FWJ  Similarly,  SYS -> SYS ->(+1) TZT    T ->     T ->(-1) SEMS -> SME ->(+1) TNF

Q: Which of the following is not purely output device? 3632 1

  • 1
    Printer
    Correct
    Wrong
  • 2
    Speaker
    Correct
    Wrong
  • 3
    Plotter
    Correct
    Wrong
  • 4
    Screen
    Correct
    Wrong
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Answer : 4. "Screen"
Explanation :

Answer: D) Screen Explanation: A touch screen is the only device which works as both an input and an output device among the given options. You view the options available to you on the screen (output) and you then use your finger to touch the option that you have chosen (input).   Hence, Screen is not purely output device.

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