Let mathrmA = [mathrma_mathrmij] be a 2 times 2 matrix such that mathrma_mathrmij in \0,1\ for all i and j. Let the random variable X denote the possible values of the determinant of the matrix A. Then, the variance of X is:

Solution & Explanation

### Related Formula Variance of a discrete random variable: textVar(X) = sum P_i X_i^2 - left(sum P_i X_iright)^2 ### Core Logic A 2 times 2 matrix with binary elements 0,1 has 2^4 = 16 total configurations. The determinant calculation yields outcomes matching values inside structural set \-1, 0, 1\. Probability distribution grid:
X_iP_iP_i X_iP_i X_i^2
-1frac316-frac316frac316
0frac101600
1frac316frac316frac316
**Total****1**sum P_i X_i = 0sum P_i X_i^2 = frac38
### Step 1: Compute Variance Plug components directly into statistical equations: textVar(X) = frac38 - (0)^2 = frac38 ### Pattern Recognition Symmetry in probability distributions centered across 0 means the expected mean mathbbE[X] evaluates to zero immediately, saving half your calculation time during variance checks. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Probability Class 12 Mathematics: Matrices and Determinants

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More Probability Previous-Year Questions — Page 6

Q19 jee_main_2024_31_jan_morning Variance of Random Variable
Three rotten apples are accidently mixed with fifteen good apples. Assuming the random variable X to be the number of rotten apples in a draw of two apples, the variance of X is
  • A. frac37153
  • B. frac57153
  • C. frac47153
  • D. frac40153

Solution

### Core Logic Total apples = 18 (3 rotten, 15 good). Random variable X = \0, 1, 2\ representing the number of rotten apples. ### Step 1: Probability Distribution P(X = 0) = frac^15C_2^18C_2 = frac105153 P(X = 1) = frac^3C_1 times ^15C_1^18C_2 = frac45153 P(X = 2) = frac^3C_2^18C_2 = frac3153 ### Step 2: Expectation E(X) = 0 times frac105153 + 1 times frac45153 + 2 times frac3153 = frac51153 = frac13 ### Step 3: Variance E(X^2) = 0 times frac105153 + 1 times frac45153 + 4 times frac3153 = frac57153 Var(X) = E(X^2) - (E(X))^2 = frac57153 - left(frac13right)^2 = frac57153 - frac17153 = frac40153 ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Maths: Probability

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