IIT JEE Practice Question and Answer

Q: Two dice are rolled simultaneously. Find the probability of getting the sum of numbers on the on the two faces divisible by 3 or 4? 1033 0

  • 1
    3/7
    Correct
    Wrong
  • 2
    7/11
    Correct
    Wrong
  • 3
    5/9
    Correct
    Wrong
  • 4
    6/13
    Correct
    Wrong
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Answer : 3. "5/9"
Explanation :

Answer: C) 5/9 Explanation: Here n(S) = 6 x 6 = 36 E={(1,2),(1,5),(2,1),(2,4),(3,3),(3,6),(4,2),(4,5),(5,1),(5,4),(6,3) ,(6,6),(1,3),(2,2),(2,6),(3,1),(3,5), (4,4),(5,3),(6,2)} => n(E)=20 Required Probability n(P) = n(E)/n(S) = 20/36 = 5/9.

Q: A train travelling at 48 kmph crosses another train, having half its length and travelling in opposite direction at 42 kmph, in 12 sec. It also covers a bridge in 45 sec. Find the length of the bridge ? 1032 0

  • 1
    250 mts
    Correct
    Wrong
  • 2
    400 mts
    Correct
    Wrong
  • 3
    320 mts
    Correct
    Wrong
  • 4
    390 mts
    Correct
    Wrong
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Answer : 2. "400 mts"
Explanation :

Answer: B) 400 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.

Q: A can do a work in 9 days, B can do a work in 7 days, C can do a work in 5 days. A works on the first day, B works on the second day and C on the third day respectively that is they work on alternate days. When will they finish the work ? 1032 0

  • 1
    [7 + (215/345)] days
    Correct
    Wrong
  • 2
    [6 + (11/215)] days
    Correct
    Wrong
  • 3
    [6 + (261/315)] days
    Correct
    Wrong
  • 4
    [5 + (112/351)] days
    Correct
    Wrong
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Answer : 3. "[6 + (261/315)] days"
Explanation :

Answer: C) [6 + (261/315)] days Explanation: After day 1, A finishes 1/9 of the work. After day 2, B finishes 1/7 more of the total work. (1/9) + (1/7) is finished. After day 3, C finishes 1/5 more of total work. Total finished is 143/315. So, after day 6, total work finished is 286/315.   Now remaining work =  29 /315   On day 7, A will work again    Work will be completed on day 7 when A is working. He must finish 29/315 of total remaining work.   Since he takes 9 days to finish the total task, he will need 261/315 of the day.    Total days required is 6 + (261/315) days.

Q: The compound interest on Rs. 8000 for 3 year at 10% p.a. is 1032 0

  • 1
    2648
    Correct
    Wrong
  • 2
    2145
    Correct
    Wrong
  • 3
    2587
    Correct
    Wrong
  • 4
    2784
    Correct
    Wrong
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Answer : 1. "2648"
Explanation :

Answer: A) 2648 Explanation: 8000 × 33.1% = 2648

Q: In how many different ways could couples be picked from 6 men and 9 women ? 1031 0

  • 1
    26
    Correct
    Wrong
  • 2
    54
    Correct
    Wrong
  • 3
    52
    Correct
    Wrong
  • 4
    28
    Correct
    Wrong
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Answer : 2. "54"
Explanation :

Answer: B) 54 Explanation: Number of mens = 8 Number of womens = 5   Different ways could couples be picked = C16× 9C1 = 9 x 6 = 54 ways.

Q: Which country has been ranked number one in pollution related deaths ? 1031 0

  • 1
    Australia
    Correct
    Wrong
  • 2
    Indonesia
    Correct
    Wrong
  • 3
    India
    Correct
    Wrong
  • 4
    Japan
    Correct
    Wrong
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Answer : 3. "India"
Explanation :

Answer: C) India Explanation:

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Answer :
Explanation :

It is given that the first digit is 1/3 of the second. There are 3 such possibilities 1)1 and 32)2 and 63)3 and 9 Now, the third digit is the sum of the first and second digits.1)1 + 3 = 4 2)2 + 6 = 83)3 + 9 = 12It is clear that option 3 is not possible. So we are left with only two options. Also, the last digit is three times the second, which rules out the second option. Hence, the answer is 1349.

Q: Which of the following is the strongest acid? 1030 0

  • 1
    ClCH2COOH
    Correct
    Wrong
  • 2
    BrCH2COOH
    Correct
    Wrong
  • 3
    FCH2COOH
    Correct
    Wrong
  • 4
    ICH2COOH
    Correct
    Wrong
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Answer : 3. "FCH2COOH"
Explanation :

Answer: C) FCH2COOH Explanation: FCH2COOH is the strongest acid out of all .Since the electron withdrawing inductive effect (-I effect) of the halogens decreases in the order   F>Cl> Br> I , therefore the acidic strength of the α- halo acids decreases in the same order.   FCH2COOH  >  ClCH2COOH   >   BrCH2COOH   >   ICH2COOH.

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