IIT JEE प्रश्न और उत्तर का अभ्यास करें

प्र: K can build a wall in 30 days. L can demolish that wall in 60 days. If K and L work on alternate days, when will the wall be completed ? 2952 1

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    120 days
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    119 days
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    118 days
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  • 4
    117 days
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उत्तर : 4. "117 days"
व्याख्या :

Answer: D) 117 days Explanation: K's work in a day(1st day) = 1/30L's work in a day(2nd day)= -1/60(demolishing)hence in 2 days, combined work= 1/30 - 1/60 =1/60since both works alternatively, K will work in odd days and L will work in even days.1/60 unit work is done in 2 days58/60 unit work will be done in 2 x 58 days = 116 daysRemaining work = 1-58/60 = 1/30Next day, it will be K's turn and K will finish the remaining 1/30 work.hence total days = 116 + 1 = 117.

प्र: Optimist is to cheerful as Pessimist is to 2951 0

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    Helpful
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    Mean
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    Petty
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  • 4
    Gloomy
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उत्तर : 4. "Gloomy"
व्याख्या :

Answer: D) Gloomy Explanation: The given words are related in a way that, an optimist is a person whose outlook is cheerful. Similarly, a pessimist is a person whose outlook is gloomy.   The answer is not (b) because a pessimist does not have to be mean. Options (c) and (a) are incorrect because neither words describe the outlook of a pessimist.   Hence, Optimist is to cheerful as Pessimist is to Gloomy.

प्र: fifteen persons are sitting around a circular table facing the centre. What is the probability that three particular persons sit together ? 2950 0

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    3/91
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    2/73
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    1/91
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    3/73
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उत्तर : 1. "3/91"
व्याख्या :

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

प्र: The circumferences of two circles are 264 meters and 352 meters. Find the difference between the areas of the larger and the smaller circles  ? 2947 0

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    2413 sq.m
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    1234 sq.m
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    4312 sq.m
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    2143 sq.m
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उत्तर : 3. "4312 sq.m"
व्याख्या :

Answer: C) 4312 sq.m Explanation: Let the radii of the smaller and the larger circles be 's' m and 'l' m respectively.    2πs = 264 and 2πl = 352      s = 2642π and l = 3522π    Difference between the areas =πl2-πs2      = π1762π2-1322π2    = 1762π-1322π     = (176 - 132)(176 + 132) / π     = (44 x 308) / (22/7) = 4312 sq.m

प्र: The gas predominantly responsible for global warming is 2947 0

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    Carbon monoxide
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    Nitrous oxide
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    Nitrogen peroxide
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    Carbondioxide
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उत्तर : 4. "Carbondioxide"
व्याख्या :

Answer: D) Carbondioxide Explanation: 72% of the totally emitted greenhouse gases is carbon dioxide.   Hence, Carbon dioxide (Co2) is predominantly responsible for Global warming.

प्र: A train moving at 2/3 rd of its normal speed reaches its destination 20 minutes late. Find the normal time taken ? 2945 0

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

Answer: B) 2/3 hrs Explanation: Let the original speed and time is S and Tthen distance = S x TNow the speed changes to 2/3S and T is T+20As the distance is sameS x T = 2/3Sx(T+20)solving this we get t = 40 minutes =40/60 = 2/3 hour

प्र: 96% of the population of a village is 23040. The total population of the village is ? 2945 0

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    24000
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    32256
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    25478
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    26587
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उत्तर : 1. "24000"
व्याख्या :

Answer: A) 24000 Explanation: Let the total population be 'P' P x (96/100) = 23040 P = 240 * 100 P = 24000.

प्र: Which of the following metals forms an amalgam with other metals  ? 2936 1

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    Mercury
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    Zinc
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    Tin
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    Lead
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उत्तर : 1. "Mercury"
व्याख्या :

Answer: A) Mercury Explanation:

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