There are 3 Indians and 3 Chinese in a group of 6 people. How many subgroups of this group can we choose so that every subgroup has at least one Indian?
56
The problem asks us to determine the number of possible subgroups from a group of 6 people, consisting of 3 Indians and 3 Chinese, such that every chosen subgroup includes at least one Indian. This is a classic combinatorial problem that can be solved using the principle of inclusion-exclusion or, more simply, by subtracting unwanted cases from the total possibilities.
We are given a group of 6 people, specifically divided into two distinct categories:
Our goal is to form subgroups. A subgroup can be of any size, from just one person up to all six people. The critical condition is that each selected subgroup must contain "at least one Indian."
To ensure a subgroup has at least one Indian, it means we cannot have subgroups that consist solely of Chinese people. This suggests a straightforward approach: calculate the total number of possible subgroups and then subtract the number of subgroups that violate our condition (i.e., those with no Indians).
The number of subgroups that can be formed from a set of 'n' distinct items is \(2^n\). This is because for each item, there are two choices: either include it in the subgroup or exclude it. This method naturally accounts for subgroups of all possible sizes, including the empty set (which usually isn't considered a "subgroup of people" in these contexts, but the formula \(2^n\) includes it. However, in this problem, removing the "no Indian" case implicitly handles the empty set as well, since it contains no Indians).
We will use the complementary counting principle:
Number of subgroups with at least one Indian = (Total number of possible subgroups from 6 people) - (Number of subgroups with no Indians)
The total number of people in the group is 6 (3 Indians + 3 Chinese). The total number of subgroups that can be formed from these 6 people is given by \(2^n\), where \(n=6\).
Total Subgroups = \(2^6\)
Total Subgroups = \(2 \times 2 \times 2 \times 2 \times 2 \times 2 = 64\)
A subgroup with no Indians means that all members of the subgroup must be Chinese. We have 3 Chinese people. The number of subgroups that can be formed using only these 3 Chinese people is \(2^k\), where \(k=3\).
Subgroups with No Indians = \(2^3\)
Subgroups with No Indians = \(2 \times 2 \times 2 = 8\)
Now, subtract the subgroups with no Indians from the total number of subgroups.
Subgroups with at least one Indian = Total Subgroups - Subgroups with No Indians
Subgroups with at least one Indian = \(64 - 8\)
Subgroups with at least one Indian = \(56\)
Here's a summary of the calculations:
| Category | Number of People Involved | Formula | Result |
|---|---|---|---|
| Total Subgroups | 6 (3 Indians + 3 Chinese) | \(2^6\) | 64 |
| Subgroups with No Indians (Only Chinese) | 3 (Chinese) | \(2^3\) | 8 |
| Subgroups with at least one Indian | Calculated | Total - No Indians | \(64 - 8 = 56\) |
Based on the calculations, there are 56 subgroups that can be chosen from the group of 6 people such that every subgroup has at least one Indian.
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