IIT JEE Practice Question and Answer

Q: A polygon has 44 diagonals, then the number of its sides are ? 1085 0

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

Answer: C) 11 Explanation: Let the number of sides be n.┬а The number of diagonals is given by┬аnC2┬а- n┬а┬а Therefore, nC2 - n = 44, n>0┬а nC2┬а- n┬а= 44 n2┬а- 3n - 88 = 0┬а n2 -11n + 8n - 88 = 0┬а┬а n(n - 11) + 8(n - 11) = 0┬а n = -8 or n = 11. ┬а As n>0, n will not be -8. Therefore, n=11.

Q: How many parallelograms will be formed if 7 parallel horizontal lines intersect 6 parallel vertical lines? 2471 0

  • 1
    215
    Correct
    Wrong
  • 2
    315
    Correct
    Wrong
  • 3
    415
    Correct
    Wrong
  • 4
    115
    Correct
    Wrong
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Answer : 2. "315"
Explanation :

Answer: B) 315 Explanation: Parallelograms are formed when any two pairs of parallel lines (where each pair is not parallel to the other pair) intersect. ┬а Hence, the given problem can be considered as selecting pairs of lines from the given 2 sets of parallel lines. ┬а Therefore, the total number of parallelograms formed = 7C2 x 6C2 = 315

Q: There are three rooms in a Hotel: one single, one double and one for four persons. How many ways are there to house seven persons in these rooms ? 3739 0

  • 1
    105
    Correct
    Wrong
  • 2
    7! x 6!
    Correct
    Wrong
  • 3
    7!/5!
    Correct
    Wrong
  • 4
    420
    Correct
    Wrong
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Answer : 1. "105"
Explanation :

Answer: A) 105 Explanation: Choose 1 person for the single room & from the remaining choose 2 for the double room & from the remaining choose 4 people for the four person room,┬а ┬аThen, 7C1 x 6C2 x 4C4┬а = 7 x 15 x 1 = 105

Q: "I am five times as old as you were, when I was as old as you are", said a man to his son. Find out their present ages, if the sum of their ages is 64 years ? 11342 0

  • 1
    Father = 50; Son =14
    Correct
    Wrong
  • 2
    Father = 40; Son =24
    Correct
    Wrong
  • 3
    Father = 60; Son =4
    Correct
    Wrong
  • 4
    Father = 48; Son =16
    Correct
    Wrong
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Answer : 2. "Father = 40; Son =24"
Explanation :

Answer: B) Father = 40; Son =24 Explanation: Let the present age of the man be 'P' and son be 'Q',Given, P + Q = 64 or Q = (64 - P)Now the man says "I am five times as old as you were, when I was as old as you are",So, P = 5[B - (P - Q)]We get 6P = 10Q,Substitute value for Q,6P = 10(64 - P),Therefore P = 40, Q = 24.

Q: Find the sum to 200 terms of the series 2 + 5 + 7 + 6 + 12 + 7 + .... 1183 0

  • 1
    30,400
    Correct
    Wrong
  • 2
    30,200
    Correct
    Wrong
  • 3
    34,600
    Correct
    Wrong
  • 4
    38,400
    Correct
    Wrong
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Answer : 1. "30,400"
Explanation :

Answer: A) 30,400 Explanation: we can treat every two consecutive terms as one.So, we will have a total of 100 terms of the nature:(2 + 5) + (7 + 6) + (12 + 7).... => 7, 13, 19,.... ┬а We know the sum of n terms┬а┬аnn+12 ┬а Now, a= 7, d=6 and n=100Hence the sum of the given series is S= 100/2 x[2 x 7 + 99 x 6]=> 50[608]=> 30,400.

Q: What least number must be substracted from 627349 so that the remaining number is divisible by 15 ? 1026 0

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

Answer: D) 4 Explanation: On dividing 627349 by 15, we get remainder = 4.Therefore, the obtained remainder is the least number to be subtracted from the given number so that the the mnumber is divisible by 15.Here 4 is the least number to be subtracted from 627349 so that it is divisible by 15.

Q: A six-digit number is formed by repeating a three-digit number; for example, 404404 or 415415 etc. Any number of this form is always exactly divisible by 1273 0

  • 1
    101
    Correct
    Wrong
  • 2
    901
    Correct
    Wrong
  • 3
    1001
    Correct
    Wrong
  • 4
    789
    Correct
    Wrong
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Answer : 3. "1001"
Explanation :

Answer: C) 1001 Explanation: Here by trial and error method, we can obseve that 404404 = 404 x 1001; 415415 = 415 x 1001, etc. So, any number of this form is divisible by 1001.

Q: A teacher multiplies 987 by a certain number and obtains 556781 as her answer. If in the answer, both 6 and 7 are wrong but the other digits are correct, then the correct answer will be 1215 0

  • 1
    553681
    Correct
    Wrong
  • 2
    555181
    Correct
    Wrong
  • 3
    556581
    Correct
    Wrong
  • 4
    555681
    Correct
    Wrong
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Answer : 4. "555681"
Explanation :

Answer: D) 555681 Explanation: Given number is 987 = 3 x 7 x 47. So, required number must be divisible by each one of 3, 7, 47. None of the numbers in 553681 and 555181 are divisible by 3. While 556581 is not divisible by 7.Correct answer is 555681.

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