Question:

If A, B, C are mutually exclusive and exhaustive events such that \(P(A):P(B):P(C)=1:l:m\), then \(P(A\cup B)+P(B\cup C)+P(C\cup A)+P(A\cup B\cup C)=\):

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For mutually exclusive events, unions reduce to simple sums.
Updated On: Jun 18, 2026
  • \( \frac{1}{3} \)
  • \( 3 \)
  • \( \frac{3}{4} \)
  • \( 1 \)
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The Correct Option is B

Solution and Explanation

Concept: For mutually exclusive and exhaustive events: \[ P(A)+P(B)+P(C)=1 \]

Step 1:
Express probabilities.
Let: \[ P(A)=x,\;P(B)=lx,\;P(C)=mx \] \[ x(1+l+m)=1 \Rightarrow x=\frac{1}{1+l+m} \]

Step 2:
Compute union expressions.
Since events are mutually exclusive: \[ P(A\cup B)=P(A)+P(B) \] Similarly: \[ P(A\cup B)+P(B\cup C)+P(C\cup A) =2(P(A)+P(B)+P(C))=2 \] Adding: \[ P(A\cup B\cup C)=1 \] \[ \Rightarrow \text{Total} = 3 \]
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