Math Problem Statement

Let A={1,2,…,14} . How many subsets of A contain exactly one element (i.e., how many singleton subsets are there)? How many doubleton subsets (containing exactly two elements) are there?

Solution

Let's solve this step by step:

1. Singleton subsets (containing exactly one element):

A singleton subset is a subset that contains exactly one element from set AA. Since A={1,2,,14}A = \{ 1, 2, \dots, 14 \} contains 14 elements, each element forms its own subset.

Thus, the number of singleton subsets is equal to the number of elements in AA, which is: Number of singleton subsets=14\text{Number of singleton subsets} = 14

2. Doubleton subsets (containing exactly two elements):

A doubleton subset is a subset that contains exactly two elements from set AA. The number of ways to choose 2 elements from 14 is given by the combination formula: (142)=14×132=91\binom{14}{2} = \frac{14 \times 13}{2} = 91

Thus, the number of doubleton subsets is: Number of doubleton subsets=91\text{Number of doubleton subsets} = 91

Final Answer:

  • Number of singleton subsets: 1414
  • Number of doubleton subsets: 9191

Would you like further details or clarifications on any of these steps?

Here are five related questions:

  1. How many subsets of AA contain exactly 3 elements?
  2. What is the total number of subsets of AA?
  3. How many subsets of AA contain at least one element?
  4. How many subsets of AA contain an even number of elements?
  5. How many subsets of AA contain more than 5 elements?

Tip: When working with subsets, combinations ((nk)\binom{n}{k}) are helpful to calculate how many ways you can choose kk elements from nn.

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Math Problem Analysis

Mathematical Concepts

Set Theory
Combinatorics
Subsets

Formulas

Combination formula: C(n, k) = n! / (k! * (n-k)!)

Theorems

Binomial Theorem (for combinations)

Suitable Grade Level

Grades 9-11