IIT JEE Practice Question and Answer

Q: If the positions of the first and the third digit within each number are interchanged, which of the following will be the third digit of the second lowest number ? 987, 514, 658, 487, 404, 269 4602 0

  • 1
    8
    Correct
    Wrong
  • 2
    9
    Correct
    Wrong
  • 3
    2
    Correct
    Wrong
  • 4
    4
    Correct
    Wrong
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Answer : 4. "4"
Explanation :

Answer: D) 4 Explanation: According to the question, after the position of the first and third digit interchanged new numbers are 789, 415, 856, 784, 404, 962 962, 856, 789, 784, 404, 415Here the second lowest number is 404 and the last digit of it is '4'.

Q: A flagstaff 17.5 m high casts a shadow of length 40.25 m. What will be the height of a building, which casts a shadow of length 28.75 m under similar conditions ? 1576 1

  • 1
    14 cm
    Correct
    Wrong
  • 2
    13.5 cm
    Correct
    Wrong
  • 3
    12.5 cm
    Correct
    Wrong
  • 4
    11.4 cm
    Correct
    Wrong
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Answer : 3. "12.5 cm"
Explanation :

Answer: C) 12.5 cm Explanation: Let the required height of the building be x meter More shadow length, More height(direct proportion) Hence we can write as (shadow length) 40.25 : 28.75 :: 17.5 : x⇒ 40.25 × x = 28.75 × 17.5⇒ x = 28.75 × 17.5/40.25= 2875 × 175/40250= 2875 × 7/1610= 2875/230= 575/46= 12.5 cm

Q: Complete the missing number in the given series. 5,  20,  76,  (—),  448 3646 0

  • 1
    185
    Correct
    Wrong
  • 2
    225
    Correct
    Wrong
  • 3
    415
    Correct
    Wrong
  • 4
    232
    Correct
    Wrong
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Answer : 2. "225"
Explanation :

Answer: B) 225 Explanation: The series follows the following pattern 5 X 5 – 5 = 20 20 X 4 – 4 = 76 76 X 3 – 3 = 225 225 X 2 – 2 = 448 Hence, the term 225 denoted by (d) completes the series

Q: A can complete a work in 12 days with a working of 8 hours per day. B can complete the same work in 8 days when working 10 hours a day. If A and B work together, working 8 hours a day, the work can be completed in --- days  ? 789 0

  • 1
    51/24
    Correct
    Wrong
  • 2
    87/5
    Correct
    Wrong
  • 3
    57/12
    Correct
    Wrong
  • 4
    60/11
    Correct
    Wrong
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Answer : 4. "60/11"
Explanation :

Answer: D) 60/11 Explanation: A can complete the work in 12 days working 8 hours a day => Number of hours A can complete the work = 12×8 = 96 hours  => Work done by A in 1 hour = 1/96   B can complete the work in 8 days working 10 hours a day => Number of hours B can complete the work = 8×10 = 80 hours  => Work done by B in 1 hour = 1/80   Work done by A and B in 1 hour = 1/96 + 1/80 = 11/480  => A and B can complete the work in 480/11 hours   A and B works 8 hours a day. Hence total days to complete the work with A and B working together  = (480/11)/ (8) = 60/11 days

Q: A box contains 4 different black balls, 3 different red balls and 5 different blue balls. In how many ways can the balls be selected if every selection must have at least 1 black ball and one red ball ? 2340 0

  • 1
    24 - 1
    Correct
    Wrong
  • 2
    2425-1
    Correct
    Wrong
  • 3
    (24-1)(23-1)25
    Correct
    Wrong
  • 4
    None
    Correct
    Wrong
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Answer : 3. "(24-1)(23-1)25"
Explanation :

Answer: C) C Explanation: It is explicitly given that all the 4 black balls are different, all the 3 red balls are different and all the 5 blue balls are different. Hence this is a case where all are distinct objects.   Initially let's find out the number of ways in which we can select the black balls. Note that at least 1 black ball must be included in each selection.   Hence, we can select 1 black ball from 4 black ballsor 2 black balls from 4 black balls.or 3 black balls from 4 black balls.or 4 black balls from 4 black balls.   Hence, number of ways in which we can select the black balls   = 4C1 + 4C2 + 4C3 + 4C4= 24-1 ........(A)   Now let's find out the number of ways in which we can select the red balls. Note that at least 1 red ball must be included in each selection.   Hence, we can select 1 red ball from 3 red ballsor 2 red balls from 3 red ballsor 3 red balls from 3 red balls   Hence, number of ways in which we can select the red balls= 3C1 + 3C2 + 3C3=23-1........(B)   Hence, we can select 0 blue ball from 5 blue balls (i.e, do not select any blue ball. In this case, only black and red balls will be there)or 1 blue ball from 5 blue ballsor 2 blue balls from 5 blue ballsor 3 blue balls from 5 blue ballsor 4 blue balls from 5 blue ballsor 5 blue balls from 5 blue balls.   Hence, number of ways in which we can select the blue balls= 5C0 + 5C1 + 5C2 + … + 5C5= 25..............(C)   From (A), (B) and (C), required number of ways=  2524-123-1

Q: Name the first state Police Officer of Nagaland who has been awarded one of the nations' military honour, ‘Shaurya Chakra’, in 2017 by the Government of India. 1302 0

  • 1
    SomviBihu
    Correct
    Wrong
  • 2
    Jong Kayi
    Correct
    Wrong
  • 3
    Nara Karom
    Correct
    Wrong
  • 4
    AtuZumvu
    Correct
    Wrong
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Answer : 4. "AtuZumvu"
Explanation :

Answer: D) AtuZumvu Explanation: For the first time since Nagaland officially gained recognition as a state, a state Police Officer AtuZumvu has been awarded one of the nations' military honour, ‘Shaurya Chakra’.

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Answer : 4. "A, B, P, U, S"
Explanation :

Answer: D) A, B, P, U, S Explanation: From the given information;  Members   Sex    Profession        A         M          Advocate     Q         F           Doctor     B         M          Advocate     R         F           Advocate     C         M          Doctor     S         F           Doctor     D         M          Doctor     T         F           Teacher     E         M          Teacher     U         F           Teacher     P         F           Doctor  Answer (D)  From option (D) A and B are two male advocates, P and S are two female doctors and u is female teacher.

Q: If the age of father is 4 years greater than the mother and 28 years greater than the son,then what is the age of the father? which one should be used to calculate the age ? 1329 0

  • 1
    mother/son = Non-prime number
    Correct
    Wrong
  • 2
    mother/son = Perfect square number A) only A alone is sufficient B) only B alone is sufficient
    Correct
    Wrong
  • 3
    both A and B are required
    Correct
    Wrong
  • 4
    A) only A alone is sufficient B) only B alone is sufficient C) both A and B are required D)
    Correct
    Wrong
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Answer : 2. "mother/son = Perfect square number A) only A alone is sufficient B) only B alone is sufficient"
Explanation :

Answer: B) only B alone is sufficient Explanation: For the given problem there are three possiblities.Father's age can be = 36, 31, 29Mother's age = 32, 27, 25Son's age = 8, 3, 1. By using only B it can be calculated.

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