IIT JEE Practice Question and Answer

Q: If A1, A2, A3, A4, ..... A10 are speakers for a meeting and A1 always speaks after, A2 then the number of ways they can speak in the meeting is 1451 0

  • 1
    9!
    Correct
    Wrong
  • 2
    9!/2
    Correct
    Wrong
  • 3
    10!
    Correct
    Wrong
  • 4
    10!/2
    Correct
    Wrong
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Answer : 4. "10!/2"
Explanation :

Answer: D) 10!/2 Explanation: As A1 speaks always after A2, they can speak only in  1st  to 9th places and    A2 can speak in 2nd to 10 the places only when A1 speaks in 1st place    A2 can speak in 9 places the remaining     A3, A4, A5,...A10  has no restriction. So, they can speak in 9.8! ways. i.e   when A2 speaks in the first place, the number of ways they can speak is 9.8!.   When A2 speaks in second place, the number of ways they can speak is  8.8!.   When A2 speaks in third place, the number of ways they can speak is  7.8!. When A2 speaks in the ninth place, the number of ways they can speak is 1.8!       Therefore,Total Number of ways they can  speak = (9+8+7+6+5+4+3+2+1) 8! = 92(9+1)8! = 10!/2

Q: The number of ways that 7 teachers and 6 students can sit around a table so that no two students are together is 1213 0

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

Answer: B) 7! x 6! Explanation: The students should sit in between two teachers. There are 7 gaps in between teachers when they sit in a roundtable. This can be done in 7P6ways. 7 teachers can sit in (7-1)! ways.    Required no.of ways is = 7P6.6! = 7!.6!

Q: The number of ways that 8 beads of different colours be strung as a necklace is 2094 0

  • 1
    2520
    Correct
    Wrong
  • 2
    2880
    Correct
    Wrong
  • 3
    4320
    Correct
    Wrong
  • 4
    5040
    Correct
    Wrong
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Answer : 1. "2520"
Explanation :

Answer: A) 2520 Explanation: The number of ways of arranging n beads in a necklace is (n-1)!2=(8-1)!2=7!2 = 2520  (since n = 8)

Q: In How many ways can the letters of the word 'CAPITAL' be arranged in such a way that all the vowels always come together? 940 0

  • 1
    360
    Correct
    Wrong
  • 2
    720
    Correct
    Wrong
  • 3
    120
    Correct
    Wrong
  • 4
    840
    Correct
    Wrong
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Answer : 1. "360"
Explanation :

Answer: A) 360 Explanation: CAPITAL = 7   Vowels = 3 (A, I, A)   Consonants = (C, P, T, L)   5 letters which can be arranged in  5P5=5!   Vowels A,I = 3!2!   No.of arrangements = 5! x 3!2!=360

Q: In how many ways the letters of the word 'DESIGN' can be arranged so that no consonant appears at either of the two ends? 1020 0

  • 1
    240
    Correct
    Wrong
  • 2
    72
    Correct
    Wrong
  • 3
    48
    Correct
    Wrong
  • 4
    36
    Correct
    Wrong
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Answer : 3. "48"
Explanation :

Answer: C) 48 Explanation: DESIGN = 6 letters   No consonants appear at either of the two ends.  = 2 x 4P4 =  2 x 4 x 3 x 2 x 1=  48

Q: Using numbers from 0 to 9 the number of 5 digit telephone numbers that can be formed is 1114 0

  • 1
    1,00,000
    Correct
    Wrong
  • 2
    59,049
    Correct
    Wrong
  • 3
    3439
    Correct
    Wrong
  • 4
    6561
    Correct
    Wrong
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Answer : 3. "3439"
Explanation :

Answer: C) 3439 Explanation: The numbers 0,1,2,3,4,5,6,7,8,9 are 10 in number while preparing telephone numbers any number can be used any number of times.   This can be done in 105ways, but '0' is there   So, the numbers starting with '0' are to be excluded is 94 numbers.    Total 5 digit telephone numbers = 105- 94 = 3439

Q: Count the number of triangles and squares in the given figure. 2724 0

  • 1
    36 triangles, 7 Squares
    Correct
    Wrong
  • 2
    38 triangles, 9 Squares
    Correct
    Wrong
  • 3
    40 triangles, 7 Squares
    Correct
    Wrong
  • 4
    42 triangles, 9 Squares
    Correct
    Wrong
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Answer : 3. "40 triangles, 7 Squares"
Explanation :

Answer: C) 40 triangles, 7 Squares Explanation: The figure may be labelled as shown      Triangles :   The Simplest triangles are BGM, GHM, HAM, ABM, GIN, IJN, JHN, HGN, IKO, KLO, LJO, JIO, KDP, DEP, ELP, LKP, BCD and AFE i.e 18 in number   The triangles composed of two components each are ABG, BGH, GHA, HAB, HGI, GIJ, IJH, JHG, JIK, IKL, KLJ,LJI, LKD, KDE, DEL and ELK i.e 16 in number.   The triangles composed of four components each are BHI, GJK, ILD, AGJ, HIL and JKE i.e 6 in number.   Total number of triangles in the figure = 18 + 16 + 6 =40.   Squares :   The Squares composed of two components each are MGNH, NIOJ, and OKPL i.e 3 in number   The Squares composed of four components each are BGHA, GIJH, IKJL and KDEL i.e 4 in number   Total number of squares in the figure = 3 + 4 =7

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Answer :
Explanation :

1. Answer : 2 Explanation : Productivity = Total production/area of Agr.land  Productivity of UP = [ (35000+30000+25000) / (30/100) ] = 300000   Productivity of MP = [ (30000+37500+27500) / (25/100) ] = 380000   Productivity of Bihar = [ (22500+27500+25000) / (20/100) ] = 375000  Productivity of Odisha = [ (22500+15000+10000) / (5/100) ]= 950000   Productivity of Haryana = [ (30000+25000+35000) / (8/100) ] = 1125000   Productivity of Punjab = [ (40000+35000+30000) / (12/100) ] = 875000  The Productivity of Haryana is the maximum.       2. Answer : 5   Explanation : Production of Punjab is maximum = 105000 tonnes      3. Answer : 3  Explanation : Production of Wheat in Punjab = 40000 tones Production of Maize in Odisha = 10000 tones Required % = (40000 - 10000)/100 = 300%      4. Answer : 4  Explanation : The ratio of prodution of Rice in Bihar to the production of Wheat in Haryana = 25000 tonnes : 25000 tonnes = 1 : 1       5. Answer : 1   Explanation : Income of MP from export of 40% of Rice at the rate of Rs.30 per kg = Rs.39crore Income of UP from export of 30% of Rice at the rate of Rs.32 per kg = Rs.28.8 crore  Required ratio = 39 : 28.8 = 390 : 288 = 65 : 48

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