Math Problem Statement

Do question 1

Do question 1

Solution

Let's solve Question 1 step by step.


Part a:

This is a binomial distribution problem, where:

  • n=11n = 11 (number of trials, i.e., stolen cars reported),
  • p=0.35p = 0.35 (probability of success, i.e., a car is found),
  • q=1p=0.65q = 1 - p = 0.65 (probability of failure).

The binomial probability formula is: P(X=k)=(nk)pkqnk,P(X = k) = \binom{n}{k} p^k q^{n-k}, where (nk)\binom{n}{k} is the binomial coefficient.


(i) Exactly three stolen cars will be found in a month:

P(X=3)=(113)(0.35)3(0.65)8P(X = 3) = \binom{11}{3} (0.35)^3 (0.65)^8 First, calculate the binomial coefficient: (113)=11!3!(113)!=11×10×93×2×1=165.\binom{11}{3} = \frac{11!}{3!(11-3)!} = \frac{11 \times 10 \times 9}{3 \times 2 \times 1} = 165. Now substitute into the formula: P(X=3)=165×(0.35)3×(0.65)8.P(X = 3) = 165 \times (0.35)^3 \times (0.65)^8. Numerical result: P(X=3)165×0.042875×0.0416520.293.P(X = 3) \approx 165 \times 0.042875 \times 0.041652 \approx 0.293.


(ii) Not more than two stolen cars will be found in a month:

This is the cumulative probability: P(X2)=P(X=0)+P(X=1)+P(X=2).P(X \leq 2) = P(X = 0) + P(X = 1) + P(X = 2).

  • For X=0X = 0: P(X=0)=(110)(0.35)0(0.65)11=(0.65)110.0137.P(X = 0) = \binom{11}{0} (0.35)^0 (0.65)^{11} = (0.65)^{11} \approx 0.0137.

  • For X=1X = 1: P(X=1)=(111)(0.35)1(0.65)10=11×0.35×(0.65)100.0809.P(X = 1) = \binom{11}{1} (0.35)^1 (0.65)^{10} = 11 \times 0.35 \times (0.65)^{10} \approx 0.0809.

  • For X=2X = 2: P(X=2)=(112)(0.35)2(0.65)9=11×102×(0.35)2×(0.65)955×0.1225×0.02710.183.P(X = 2) = \binom{11}{2} (0.35)^2 (0.65)^9 = \frac{11 \times 10}{2} \times (0.35)^2 \times (0.65)^9 \approx 55 \times 0.1225 \times 0.0271 \approx 0.183.

Summing up: P(X2)=0.0137+0.0809+0.1830.2776.P(X \leq 2) = 0.0137 + 0.0809 + 0.183 \approx 0.2776.


Part b:

This is a Poisson distribution problem, where:

  • The average rate λ=3\lambda = 3 (books per year).

The Poisson probability formula is: P(X=k)=λkeλk!.P(X = k) = \frac{\lambda^k e^{-\lambda}}{k!}.


(i) Exactly three books in a given year:

P(X=3)=33e33!=27e36.P(X = 3) = \frac{3^3 e^{-3}}{3!} = \frac{27 e^{-3}}{6}. Using e30.0498e^{-3} \approx 0.0498: P(X=3)27×0.049860.224.P(X = 3) \approx \frac{27 \times 0.0498}{6} \approx 0.224.


(ii) At least one book in a two-year period:

For two years, the average rate λ=6\lambda = 6. The complement of "at least one book" is "no books": P(X1)=1P(X=0),P(X \geq 1) = 1 - P(X = 0), where: P(X=0)=60e60!=e6.P(X = 0) = \frac{6^0 e^{-6}}{0!} = e^{-6}. Using e60.00248e^{-6} \approx 0.00248: P(X1)=10.002480.9975.P(X \geq 1) = 1 - 0.00248 \approx 0.9975.


(iii) Less than three books in half a year:

For half a year, the average rate λ=1.5\lambda = 1.5. P(X<3)=P(X=0)+P(X=1)+P(X=2).P(X < 3) = P(X = 0) + P(X = 1) + P(X = 2).

  • For X=0X = 0: P(X=0)=1.50e1.50!=e1.50.2231.P(X = 0) = \frac{1.5^0 e^{-1.5}}{0!} = e^{-1.5} \approx 0.2231.

  • For X=1X = 1: P(X=1)=1.51e1.51!=1.5×e1.50.3346.P(X = 1) = \frac{1.5^1 e^{-1.5}}{1!} = 1.5 \times e^{-1.5} \approx 0.3346.

  • For X=2X = 2: [ P(X = 2) = \frac{1.5^2 e^{-1.5}}{2!} = \frac{2.25 \times e^{-1.5}}{2

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Math Problem Analysis

Mathematical Concepts

Binomial Distribution
Poisson Distribution
Normal Distribution
Probability Theory

Formulas

Binomial probability formula: P(X = k) = C(n, k) * p^k * (1 - p)^(n - k)
Poisson probability formula: P(X = k) = (λ^k * e^(-λ)) / k!
Standard normal distribution: Z = (X - μ) / σ

Theorems

Binomial Coefficient
Complement Rule
Properties of Normal Distribution

Suitable Grade Level

Undergraduate Level