Question:

Let \( S \) be a set consisting of 10 elements.
The number of tuples of the form \( (A, B) \) such that \( A \) and \( B \) are subsets of \( S \), and \( A \subseteq B \), is \(\underline{\hspace{2cm}}\).

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For counting pairs \( (A,B) \) with \( A \subseteq B \), count choices per element instead of subsets separately.
Updated On: Feb 2, 2026
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Correct Answer: 59049

Solution and Explanation

Let \( S \) have 10 elements. For each element of \( S \), there are three possible choices:
- The element is not in \( B \)
- The element is in \( B \) but not in \( A \)
- The element is in both \( A \) and \( B \)
Since \( A \subseteq B \), an element cannot be in \( A \) without being in \( B \).
Thus, each element has exactly 3 independent choices.
Therefore, the total number of such ordered pairs \( (A, B) \) is: \[ 3^{10} = 59049 \] Final Answer: \[ \boxed{59049} \]
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