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If some or all of n objects are taken at...

If some or all of n objects are taken at a time, then the number of combinations is `2^(n) - 1`.

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To solve the problem, we need to find the sum of combinations of n objects taken at a time, specifically \( \binom{n}{1} + \binom{n}{2} + \binom{n}{3} + \ldots + \binom{n}{n} \). ### Step-by-Step Solution: 1. **Understanding the Binomial Theorem**: The Binomial Theorem states that: \[ (A + B)^n = \sum_{k=0}^{n} \binom{n}{k} A^{n-k} B^k \] For our case, we can set \( A = 1 \) and \( B = 1 \). 2. **Applying the Binomial Theorem**: Substituting \( A \) and \( B \) into the Binomial Theorem gives us: \[ (1 + 1)^n = \sum_{k=0}^{n} \binom{n}{k} 1^{n-k} 1^k \] This simplifies to: \[ 2^n = \sum_{k=0}^{n} \binom{n}{k} \] 3. **Identifying the Terms**: The sum \( \sum_{k=0}^{n} \binom{n}{k} \) includes all combinations from 0 to n. We can express this as: \[ \binom{n}{0} + \binom{n}{1} + \binom{n}{2} + \ldots + \binom{n}{n} = 2^n \] 4. **Separating the Terms**: We know that \( \binom{n}{0} = 1 \). Therefore, we can rewrite the equation: \[ 1 + \left( \binom{n}{1} + \binom{n}{2} + \ldots + \binom{n}{n} \right) = 2^n \] 5. **Isolating the Desired Sum**: To find the sum \( \binom{n}{1} + \binom{n}{2} + \ldots + \binom{n}{n} \), we subtract 1 from both sides: \[ \binom{n}{1} + \binom{n}{2} + \ldots + \binom{n}{n} = 2^n - 1 \] 6. **Conclusion**: Thus, we have shown that the sum of combinations of n objects taken at a time (from 1 to n) is: \[ \binom{n}{1} + \binom{n}{2} + \ldots + \binom{n}{n} = 2^n - 1 \] ### Final Result: The number of combinations when taking some or all of n objects at a time is \( 2^n - 1 \).
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