GATE Practice Question and Answer

Q: fifteen persons are sitting around a circular table facing the centre. What is the probability that three particular persons sit together ? 2303 0

  • 1
    3/91
    Correct
    Wrong
  • 2
    2/73
    Correct
    Wrong
  • 3
    1/91
    Correct
    Wrong
  • 4
    3/73
    Correct
    Wrong
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Answer : 1. "3/91"
Explanation :

Answer: A) 3/91 Explanation: In a circle of n different persons, the total number of arrangements possible = (n - 1)!Total number of arrangements = n(S) = (15 – 1)! = 14 !Taking three persons as a unit, total persons = 13 (in 4 units)Therefore no. of ways for these 13 persons to around the circular table = (13 - 1)! = 12!In any given unit, 3 particular person can sit in 3!. Hence total number of ways that any three person can sit =n(E) = 12! X 3!Therefore P (E) = probability of three persons sitting together = n(E) / n(S) = 12! X 3 ! / 14!= 12!x3x2 / 14x13x12! = 6/14x13 = 3/91

Q: A number of cats got together and decided to kill between them 999919 rats. Every cat killed an equal number of rats. Each cat killed more rats than there were cats. How many rats do you think that each cat killed ? 6170 0

  • 1
    1009
    Correct
    Wrong
  • 2
    991
    Correct
    Wrong
  • 3
    2000
    Correct
    Wrong
  • 4
    1000
    Correct
    Wrong
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Answer : 1. "1009"
Explanation :

Answer: A) 1009 Explanation: Given total number of rats = 999919   999919 = 1000000 - 81 = 10002 - 92 = (1000+9)(1000-9) = 1009 x 991.Since there were more rats than there were cats, 991 cats killed 1009 rats each.

Q: How many 6-digit even numbers can be formed from the digits 1, 2, 3, 4, 5, 6 and 7 so that the digits should not repeat and the second last digit is even ? 2224 0

  • 1
    521
    Correct
    Wrong
  • 2
    720
    Correct
    Wrong
  • 3
    420
    Correct
    Wrong
  • 4
    225
    Correct
    Wrong
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Answer : 2. "720"
Explanation :

Answer: B) 720 Explanation: Let last digit is 2when second last digit is 4 remaining 4 digits can be filled in 120 ways, similarly second last digit is 6 remained 4 digits can be filled in 120 ways.so for last digit = 2, total numbers=240   Similarly for 4 and 6When last digit = 4, total no. of ways =240and last digit = 6, total no. of ways =240so total of 720 even numbers are possible.

Q: A man spend Rs. 810 in buying trouser at Rs. 70 each and shirt at Rs. 30 each. What will be the ratio of trouser and shirt when the maximum number of trouser is purchased ? 3078 0

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

Answer: C) 3:2 Explanation: Let us assume S as number of shirts and T as number of trousersGiven that each trouser cost = Rs.70 and that of shirt = Rs.30Therefore, 70 T + 30 S = 810=> 7T + 3S = 81......(1)T = ( 81 - 3S )/7 We need to find the least value of S which will make (81 - 3S) divisible by 7 to get maximum value of TSimplifying by taking 3 as common factor i.e, 3(27-S) / 7In the above equation least value of S as 6 so that 27- 3S becomes divisible by 7 Hence T = (81-3xS)/7 = (81-3x6)/7 = 63/7 = 9 Hence for S, put T in eq(1), we getS = 81-7(9)/3 = 81-63 / 3 = 18/3 = 6.The ratio of T:S = 9:6 = 3:2.

Q: A wholesale dealer allows a discount of 20 % on the marked price to the retailer. The retailer sells at 5% below the marked price. If the customer pays Rs.19 for an article, what profit is made by the retailer on it ? 1284 0

  • 1
    Rs. 4
    Correct
    Wrong
  • 2
    Rs. 3
    Correct
    Wrong
  • 3
    Rs. 5
    Correct
    Wrong
  • 4
    Rs. 1
    Correct
    Wrong
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Answer : 2. "Rs. 3"
Explanation :

Answer: B) Rs. 3 Explanation: Let wholesaler dealers marked price = 100%, Retailer's C.P = 80% And the retailer sells at 5% less than the marked price => S.P = 95%If S.P of 95% of the retailer costs Rs.19 to customer,so its C.P of 80% will cost 80 x 19/95 = 16 Profit made by the retailer = 19-16 =  Rs.3

Q: The top and bottom of a tower were seen to be at angles of depression 30° and 60° from the top of a hill of height 100 m. Find the height of the tower ? 1717 1

  • 1
    42.2 mts
    Correct
    Wrong
  • 2
    33.45 mts
    Correct
    Wrong
  • 3
    66.6 mts
    Correct
    Wrong
  • 4
    58.78 mts
    Correct
    Wrong
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Answer : 3. "66.6 mts"
Explanation :

Answer: C) 66.6 mts Explanation: From above diagramAC represents the hill and DE represents the tower Given that AC = 100 m angleXAD = angleADB = 30° (∵ AX || BD ) angleXAE = angleAEC = 60° (∵ AX || CE) Let DE = h Then, BC = DE = h, AB = (100-h) (∵ AC=100 and BC = h), BD = CE tan 60°=AC/CE => √3 = 100/CE =>CE = 100/√3 ----- (1) tan 30° = AB/BD => 1/√3 = 100−h/BD => BD = 100−h(√3)∵ BD = CE and Substitute the value of CE from equation 1 100/√3 = 100−h(√3) => h = 66.66 mts The height of the tower = 66.66 mts.

Q: 5/9 of the part of the population in a village are females. If 30 % of the females are married. The percentage of unmarried males in the total males is ? 1486 0

  • 1
    62.5 %
    Correct
    Wrong
  • 2
    125 %
    Correct
    Wrong
  • 3
    84.32 %
    Correct
    Wrong
  • 4
    46.87 %
    Correct
    Wrong
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Answer : 1. "62.5 %"
Explanation :

Answer: A) 62.5 % Explanation: Let total population = p number of females = 5p/9number of males =(p-5p/9) = 4p/9married females = 30% of 5p/9 = 30x5p/100x9 = p/6married males = p/6unmarried males =(4p/9-p/6) = 5p/18Percentage of unmarried males in the total males = {(5p/18)/4p/9}x100 = (5p/18)x(9/4p) = 125/2 % = 62.5%

Q: A sum of Rs. 427 is to be divided among A, B and C in such a way that 3 times A’s share, 4 times B’s share and 7 times C’s share are all equal. The share of C is ? 5323 0

  • 1
    64
    Correct
    Wrong
  • 2
    76
    Correct
    Wrong
  • 3
    84
    Correct
    Wrong
  • 4
    98
    Correct
    Wrong
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Answer : 3. "84"
Explanation :

Answer: C) 84 Explanation: Given total sum = Rs. 427And given that 3 times A’s share, 4 times B’s share and 7 times C’s share are all equal.=> 3A = 4B = 7CBut given=> A + B + C = 427Now express A and B in terms of C i.e=> (7C/3) + (7C/4) + C = 427=> C = 84

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