Hyperbola
Grade 11

Question:

<p>Two dice are thrown independently. Let A be the event that the number appeared on the <span class="math-tex">\(1^{\text {st }}\)</span> die is less than the number appeared on the <span class="math-tex">\(2^{\text {nd }}\)</span> die, B be the event that the number appeared on the <span class="math-tex">\(1^{\text {st }}\)</span> die is even and that on the second die is odd, and C be the event that the number appeared on the <span class="math-tex">\(1^{\text {st }}\)</span> die is odd and that on the <span class="math-tex">\(2^{\text {nd }}\)</span> is even. Then:</p>
<p style="display:inline">The number of favourable cases of the event <span class="math-tex">\((A \cup B) \cap C\)</span> is 6</p>
<p style="display:inline">B and C are independent</p>
<p style="display:inline">A and B are mutually exclusive</p>
<p style="display:inline">The number of favourable cases of the events <span class="math-tex">\(A, B\)</span> and <span class="math-tex">\(C\)</span> are 15, 6 and 6 respectively</p>

Step-by-Step Solution

Key Concept: The independence of events is strictly determined by verifying if the probability of their intersection equals the product of their individual probabilities through systematic enumeration of favorable outcomes.
<p>Here,<br /> <span class="math-tex">${A}=\{(1,2),(1,3),(1,4),(1,5),(1,6),(2,3),(2,4),$</span>&nbsp;(2,5),(2,6),(3,4),(3,5),(3,6),(4,5),(4,6),(5,6)}<br /> <span class="math-tex">$\therefore n({~A})=15$</span><br /> <span class="math-tex">${B}=\{(2,1),(2,3),(2,5),(4,1),(4,3),(4,5),$</span>&nbsp;(6,1),(6,3),(6,5)}<br /> <span class="math-tex">$\therefore n({~B})=9$</span><br /> <span class="math-tex">${C}=\{(1,2),(1,4),(1,6),(3,2),(3,4),(3,6),$</span>&nbsp;(5,2),(5,4),(5,6)}<br /> <span class="math-tex">$\therefore n(c)=9$</span></p> <ol> <li>&nbsp;False, <span class="math-tex">$n({~A})=15, n({~B})=9 \neq 6, n({c})=9 \neq 6$</span></li> <li><span class="math-tex">$({A} \cap {C})=\{(1,2),(1,4),(1,6),(3,4),(3,6),(5,6)\}$</span><br /> <span class="math-tex">$\therefore n({~A} \cap {C})=6$</span><br /> <span class="math-tex">$({B} \cap {C})=\phi$</span><br /> <span class="math-tex">$\therefore n({~B} \cap {C})=0$</span><br /> and <span class="math-tex">$n(({~A} \cup {~B}) \cap {C})=6$</span></li> <li><span class="math-tex">${P}({B})=\frac{9}{36}=\frac{1}{4}, {P}({C})=\frac{9}{36}=\frac{1}{4}, {P}({B} \cap {C})=0$</span><br /> As, <span class="math-tex">${P}({B}) \cdot {P}({C}) \neq {P}({B} \cap {C})$</span><br /> So, B and C are not independent.</li> <li>As, <span class="math-tex">${A} \cap {B}=\{(4,5)\} \neq \phi$</span><br /> So, A and B are not exclusive events.</li> </ol>
Correct Answer: A

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