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Exercise 14.1 · Q1

Q.A die is rolled. Let E be the event 'die shows 4' and F be the event 'die shows even number'. Are E and F mutually exclusive?

Rajasthan RbseTextbookSubjective· 2mImportance★★★★★
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Two events are mutually exclusive if they cannot happen together. Here, the event "die shows 4" is a subset of the event "die shows an even number", so they can occur simultaneously — hence they are not mutually exclusive.

The core idea is simple: mutually exclusive events have no outcomes in common. If one event happening forces the other to be impossible, they are mutually exclusive. But if one event is actually a special case of the other, they can definitely happen together.

Let’s check this with the die roll.

  1. Define the sample space.

    A standard die has six faces: S={1,2,3,4,5,6}S = \{1, 2, 3, 4, 5, 6\}.

  2. Write down the events clearly.

    • EE: die shows 4. So E={4}E = \{4\}.
    • FF: die shows an even number. So F={2,4,6}F = \{2, 4, 6\}.
  3. Check for common outcomes.

    The intersection E∩FE \cap F is the set of outcomes that belong to both events.

    E∩F={4}∩{2,4,6}={4}E \cap F = \{4\} \cap \{2, 4, 6\} = \{4\}.

    Since {4}\{4\} is not empty, the events share an outcome.

  4. Interpret the result.

    If the die shows 4, both EE and FF occur together. That means they are not mutually exclusive. Mutually exclusive events would have E∩F=∅E \cap F = \varnothing (the empty set).

Watch out

A common mistake is to think that because "4" is a single number and "even numbers" are many, they must be different events. But "4" is itself an even number — so it belongs to both sets. Always check the actual elements, not just the descriptions.

Tip

A quick way to see this: if one event is a subset of the other (here E⊂FE \subset F), they can never be mutually exclusive unless the subset is empty. Because every outcome in the smaller event is also in the larger one.

✓Final answer

The events EE and FF are not mutually exclusive because they share the outcome {4}\{4\}.

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