IIT JEE प्रश्न और उत्तर का अभ्यास करें

प्र: A polygon has 44 diagonals, then the number of its sides are ? 1207 0

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    13
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    9
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  • 3
    11
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  • 4
    7
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उत्तर : 3. "11"
व्याख्या :

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

प्र: How many parallelograms will be formed if 7 parallel horizontal lines intersect 6 parallel vertical lines? 2737 0

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    215
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    315
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    415
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  • 4
    115
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उत्तर : 2. "315"
व्याख्या :

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.   Hence, the given problem can be considered as selecting pairs of lines from the given 2 sets of parallel lines.   Therefore, the total number of parallelograms formed = 7C2 x 6C2 = 315

प्र: 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 ? 3991 0

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    105
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  • 2
    7! x 6!
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  • 3
    7!/5!
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  • 4
    420
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उत्तर : 1. "105"
व्याख्या :

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,   Then, 7C1 x 6C2 x 4C4  = 7 x 15 x 1 = 105

प्र: "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 ? 11484 0

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    Father = 50; Son =14
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    Father = 40; Son =24
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    Father = 60; Son =4
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  • 4
    Father = 48; Son =16
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उत्तर : 2. "Father = 40; Son =24"
व्याख्या :

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.

प्र: Find the sum to 200 terms of the series 2 + 5 + 7 + 6 + 12 + 7 + .... 1285 0

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    30,400
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  • 2
    30,200
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  • 3
    34,600
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  • 4
    38,400
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उत्तर : 1. "30,400"
व्याख्या :

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,....   We know the sum of n terms  nn+12   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.

प्र: What least number must be substracted from 627349 so that the remaining number is divisible by 15 ? 1130 0

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    1
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    2
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    3
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    4
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उत्तर : 4. "4"
व्याख्या :

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.

प्र: 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 1424 0

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    101
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  • 2
    901
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  • 3
    1001
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    789
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उत्तर : 3. "1001"
व्याख्या :

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.

प्र: 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 1375 0

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    553681
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    555181
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    556581
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  • 4
    555681
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उत्तर : 4. "555681"
व्याख्या :

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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