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KVPY Class-XI (SA) - 06-11-2016

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KVPY Class-XI (SA) - 06-11-2016
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  • Question 1
    1 / -0

    The number of digits in the decimal expansion of 165516 is

    Solution

    165516
    = 16 × 164 × 516
    = 16 × 1016
    It is an 18 digit number.

     

  • Question 2
    1 / -0

    Let t be a real number such that t2 = at + b for some positive integers a and b. Then for any choice of positive integers a and b, t3 is never equal to

    Solution

    t2 = at + b ; a, b ∈ I+
    t3 = at2 + bt
    = a(at + b) + bt
    = a2 t + bt + ab
     t3 = (a2 + b)t + ab , check possibility for a, b ∈ I+ from options.
    (1) a2 + b = 4
    ab = 3 possible for (a = 1, b = 3)
    (2) a2 + b = 8
    ab = 5 not possible
    (3) a2 + b = 10
    ab = 3 possible (a = 3, b = 1)
    (4) a2 + b = 6
    ab = 5 possible (a = 1, b = 5)

     

  • Question 3
    1 / -0

    Consider the equation (1 + a + b)2 = 3(1 + a2 + b2), where a, b are real numbers. Then

    Solution

    (1 + a + b)2 = 3 (1 + a2 + b2 )
    1 + a2 + b2 + 2a + 2ab + 2b = 3 + 3a2 + 3b2
    . a + a . b + 1 . b = 12 + a2 + b2
    So, 1 = a = b is the only possible solution pair.

     

  • Question 4
    1 / -0

    Consider a cuboid, all of whose edges are integers and whose base is a square. Suppose the sum of all its edges is numerically equal to the sum of the areas of all its six faces. Find the sum of all its edges.

    Solution

    Let the sides be a, a and h.
    So, 4a + 4h + 4a = 2(a2 + ah + ah)
    2a + 2h + 2a = a2 + 2ah
    ⇒ a2 - 4a = 2h - 2ah
    ⇒ (a2 - 1) + 1 - 4(a - 1) - 4 = 2h(1 - a)
    ⇒ (a - 1)(a + 1) - 4(a - 1) - 3 = 2h(1 - a)
    ⇒ 2h = 3/a - 1 + 4 - (a + 1)
    So, a = 2 and h = 2 are the only integral solution (a and h are positive integers).
    Sum of all edges = (4 × 2) + (4 × 2) + (4 × 2) = 24

     

  • Question 5
    1 / -0

    Find the number of all 2-digit numbers 'n', such that 'n' is equal to the sum of the square of digit in its tens place and the cube of the digit in its units place.

    Solution

    n = ab
    ab = a2 + b3
    ⇒ 10a + b = a2 + b3
    ⇒ a(10 - a) + b(1 - b)(1 + b) = 0
    ⇒ a(10 - a) = (b - 1)(b) (b + 1)
    If b = 2; a(10 - a) = 6 ⇒ No value of 'a'
    If b = 3; a(10 - a) = 24 ⇒ a ∈ {4, 6}
    {The numbers are 43 and 63.}
    b = 4; a(10 - a) = 60 ⇒ No value of a
    b = 5; a(10 - a) = 120 ⇒ No need to check further
    ∴ The numbers are 43 and 63.

     

  • Question 6
    1 / -0

    Let f be a function defined on the set of all positive integers such that f(xy) = f(x) + f(y) for all positive integers x and y. If f(12) = 24 and f(8) = 15, then the value of f(48) is

    Solution

    f(xy) = f(x) + f(y)
    ⇒ f(x) = logax
    So, f(12) = 24
    ⇒ loga12 = 24
    ⇒ 12 = a24 and f(8) = 15
    ⇒ loga8 = 15
    ⇒ 3loga2 = 15
    ⇒ loga2 = 5
    So, f(48) = loga48 = loga12 + loga4
    = loga12 + loga22
    = 24 + 2 . 5
    = 34

     

  • Question 7
    1 / -0

    The primary and the secondary coil of a transformer contain 10 and 100 turns, respectively. The primary coil is connected to a battery that supplies a constant voltage of 1.5 volts. The voltage across the secondary coil is

    Solution

    Since the voltage production is based upon A.C. supply and this voltage is D.C, which is constant, no flux will change in secondary and no voltage will be induced.

     

  • Question 8
    1 / -0

    Mercury is often used in clinical thermometers. Which one of the following properties of mercury is not a reason for this?

    Solution

    High density is not the reason for its uses in clinical thermometers.

     

  • Question 9
    1 / -0

    LiOH reacts with CO2 to form Li2CO3 (atomic mass of Li = 7). The amount of CO2 (in g) consumed by 1 g of LiOH is closest to

    Solution

    2LiOH + CO2 → Li2CO3 + H2O

    Number of moles of Li = 1/24
    Number of moles of CO2 used = 1/48
    Mass of CO2 = 1/48 × 44 = 0.916 g

     

  • Question 10
    1 / -0

    Among the elements Li, N, C and Be, one with the largest atomic radius is

    Solution

    As we move from left to right in a period atomic, radius decrease due to increase in Zeff. So, the largest radius is of lithium.

     

  • Question 11
    1 / -0

    What is the length of human DNA containing 6.6 x 109 bp?

    Solution

    The distance between 2 nucleotides/nitrogen bases is 3.4 angstroms and human DNA containing 6.6 x 109 bp multiplied by this distance gives a length of 2.2 meters

     

  • Question 12
    1 / -0

    The Diptheria, Pertussis, Tetanus (DPT) vaccine consists of

    Solution

    Vaccine of Diphtheria, Pertussis and Tetanus (DPT) consists of
    (i) Toxoids of Diptheria and Tetanus
    (ii) Heat killed cells of Pertussis

     

  • Question 13
    1 / -0

    Which of the following is NOT an enzyme?

    Solution

    Lipase = Enzyme (Lipid digesting)
    Amylase = Enzyme (Starch digesting)
    Trypsin = Enzyme (Endopeptidase)
    Bilirubin = Bile pigment

     

  • Question 14
    1 / -0

    The pH of the avian blood is maintained by

    Solution

    The bicarbonate buffer system is an acid-base mechanism involving the balance of carbonic acid, bicarbonate ion and carbon dioxide in order to maintain pH in the blood. The pH of avian blood is maintained by bicarbonate ion.

     

  • Question 15
    1 / -0

    Podocyte layer that provides outer lining to the surface of glomerular capillaries is found in

    Solution

    Podocytes are cells of squamous epithelium of bowman's capsule of nephrons.

     

  • Question 16
    1 / -0

    If a dsDNA has 20% adenine, what would be its cytosine content?

    Solution

    According to Chargaffs rule, the molar concentration of purines is equal to molar concentration of pyrimidines.
    A + G = T + C
    So, if Adenine is 20%, then T is also 20% because A always pairs with T, total of 40%, which we then subtract from 100%, leaving us with 60%. Because cytosine and guanine are complimentary base pairs, we now have the answer to the amount of guanine in this DNA sequence: 30%
    Hence, G is 30% and C is also 30%.

     

  • Question 17
    1 / -0

    Which one of the following is incapable of curing Pellagra?

    Solution

    Pellagra can be cured by - Niacin
    - Nicotinamide
    - Tryptophan
    Tryptophan is a precursor of Niacin. All three can prevent pellagra.

     

  • Question 18
    1 / -0

    In Escherichia coli, how many codons code for the standard amino-acids?

    Solution

    In all living organisms, there are 64 codons and 3 codons are stop or termination codons, i.e. UAA, UAG and UGA which do not code for any amino acids.

     

  • Question 19
    1 / -0

    Bombyx mori (silk worm) belongs to the order

    Solution

    Order of Silkworm ⇒ Lepidoptera
    (Bombax mori)

     

  • Question 20
    1 / -0

    The source of mammalian hormone 'Relaxin' is

    Solution

    Relaxin is a hormone secreted by the placenta that causes the cervix to dilate and prepares the uterus for the action of oxytocin during labour.

     

  • Question 21
    1 / -0

    Which one of the following animals is a connecting link between reptiles and mammals?

    Solution

    The connecting links between reptiles and mammals are:
    (1) Platypus
    (2) Echidna

     

  • Question 22
    1 / -0

    What is the number of chromosomes in an individual with Turner's syndrome?

    Solution

    The genetic makeup of Turner's syndrome is 44 + XO. So, there are a total of 45 chromosomes only.

     

  • Question 23
    1 / -0

    Chipko movement in the year 1974 in Garhwal Himalayas involved

    Solution

    Chipko movement was headed by social activist Sunder Lal Bahuguna in Uttarakhand to save trees from felling.

     

  • Question 24
    1 / -0

    Which of the following amino acids is NOT involved in gluconeogenesis?

    Solution

    The primary carbon skeletons used for gluconeogenesis are derived from pyruvate, lactate, glycerol, and the amino acids alanine and glutamine. Lysine cannot be converted to glucose.

     

  • Question 25
    1 / -0

    Which of the following entities causes syphilis?

    Solution

    Causative agent of Syphilis is Treponema pallidum.

     

  • Question 26
    1 / -0

    If 'a' is a positive real number such that a5 - a3 + a = 2, then

    Solution

    a5 - a3 + a = 2; a ∈ R+
    Let f(a) = a5 - a3 + a - 2; {Note f'(a) > 0 ∀ a ∈ R+}
    For a6 = 3,
    a = 31/6 = 1.2 {use calculator}
    We get f(1.2) < 0
    At a = 41/6,
    f(41/6) > 0
    So, one root in a6 ∈ (3, 4)

     

  • Question 27
    1 / -0

    Consider the quadratic equation nx2 - 7√nx + n = 0, where n is a positive integer. Which of the following statements is/are necessarily correct?

    I. For any n, the roots are distinct.
    II. There are infinitely many values of n for which both roots are real.
    III. The product of the roots is necessarily an integer.

    Solution

    nx2 - 7√nx + n = 0, where n is a positive integer.

    D = 49n - 4n2

    = n(49 - 4n)

    D ≠ 0 for any n ∈ I+. So, the roots are distinct.

    For roots to be real, D ≥ 0

    So, n ≤ 49/9

    So, n can be {1, 2, 3, ...,12}

    Clearly, the product of the roots is 1.

     

  • Question 28
    1 / -0

    If a 3-digit number is randomly chosen, what is the probability that either the number itself or some permutation of the number (which is a 3-digit number) is divisible by 4 and 5?

    Solution

    We need a 3-digit number which is divisible by 4 and 5 both.
    i.e. Their last two digits are: 00, 20, 40, 60 and 80.
    Now, ending with 00 are:
    {100, 200, 900}
    If a digit repeats other than '0', then they are:
    {220, 440, 660, 880}
    But 220 can be permuted according to the condition as {220, 202}.
    So, there are '8' other favorable cases.
    If the number has no digit repeated, like 320:
    320 can be permuted in 4 ways.
    {302, 230, 320, 203}
    So, such numbers are: 8 x 4 x 4 = 128
    Total favourable cases = 9 + 8 + 128 = 145
    So, required probability = 145/900 = 29/180 

     

  • Question 29
    1 / -0

    The atmospheric pressure is 760 mm Hg at the sea level. Which of the following ranges is nearest to the partial pressure of CO2 in mm Hg?

    Solution

    The partial pressure of carbon dioxide in outside air (dry air at sea level) is 0.3 mm Hg.

     

  • Question 30
    1 / -0

    Match the different types of heart given in column A with organisms given in column B. Choose the correct combination.

    Column A Column B
    P. Neurogenic heart i. Human
    Q. Bronchial heart ii. King crab
    R. Pulmonary heart iii. Shark
    Solution

    Neurogenic heart → King crab

    Bronchial heart → Shark

    Pulmonary heart → Human

     

  • Question 31
    1 / -0

    Match the enzymes in Group I with the reactions in Group II. Select the correct combination.

    Group I Group II
    P. Hydrolase i. Inter-conversion of optical isomers
    Q. Lyase ii. Oxidation and reduction of two substrates
    R. Isomerase iii. Joining of two compounds
    S. Ligase iv. Removal of a chemical group from a substrate
      v. Cleave the substrate by uptake of water molecule
    Solution

    (i) Hydrolase catalyses the hydrolysis of ester, ether, peptide, glycosidic, C-C, C-halide or P-N bonds.
    (ii) Lyase catalyses the breaking of chemical groups other than hydrolysis.
    (iii) Isomerase catalyses the inter-conversion of optical, geometric or positional isomers.
    (iv) Ligase catalyses the linking together of two compounds.

     

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