PYQ Vault

Day 83: NDA Maths

5 questions. Try each one first, then open its answer.

  1. Question 1

    Logarithms. This type asked 2 times: NDA 1 2018, NDA 1 2021. This one: NDA 1 2018

    19
    What is 1log⁡2N+1log⁡3N+⋯+1log⁡100N\frac{1}{\log_{2}N} + \frac{1}{\log_{3}N} + \cdots + \frac{1}{\log_{100}N} equal to (N≠1)(N \ne 1)?

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  2. Question 2

    Matrices & Determinants. This type asked 2 times: NDA 2 2018, NDA 1 2021. This one: NDA 1 2021

    7
    If a1,a2,a3,…,a9a_1, a_2, a_3, \ldots, a_9 are in GP, then what is the value of ∣ln⁡a1ln⁡a2ln⁡a3ln⁡a4ln⁡a5ln⁡a6ln⁡a7ln⁡a8ln⁡a9∣\begin{vmatrix}\ln a_1 & \ln a_2 & \ln a_3\\\ln a_4 & \ln a_5 & \ln a_6\\\ln a_7 & \ln a_8 & \ln a_9\end{vmatrix}?

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  3. Question 3

    Matrices & Determinants. This type asked 2 times: NDA 2 2019, NDA 1 2021. This one: NDA 1 2021

    18
    If the determinant ∣x130011x4∣=0\begin{vmatrix}x & 1 & 3\\0 & 0 & 1\\1 & x & 4\end{vmatrix} = 0, then what is xx equal to?

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  4. Question 4

    Probability. This type asked 2 times: NDA 1 2020, NDA 1 2021. This one: NDA 1 2021

    115
    If P(A∪B)=56P(A\cup B)=\frac{5}{6}, P(A∩B)=13P(A\cap B)=\frac{1}{3} and P(Aˉ)=12P(\bar{A})=\frac{1}{2}, then which of the following is/are correct? 1. AA and BB are independent events. 2. AA and BB are mutually exclusive events.

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  5. Question 5

    Statistics. This type asked 2 times: NDA 1 2017, NDA 1 2021. This one: NDA 1 2021

    112
    The mean of 12 observations is 75. If two observations are discarded, then the mean of the remaining observations is 65. What is the mean of the discarded observations?

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