Step 1: Form a group of 2
Choose 2 people out of the total 8.- 8C2 = (8 * 7) / (2 * 1) = 28 ways
Step 2: Form the first group of 3
From the remaining 6 people, choose 3.- 6C3 = (6 * 5 * 4) / (3 * 2 * 1) = 20 ways
Step 3: Form the final group of 3
The remaining 3 people automatically form the last group.This gives 28 × 20 = 560 arrangements.
However, the two 3-member groups are identical in size, so each division has been counted twice.
Therefore, the required number of ways = 560 ÷ 2 = 280.
Answer: BExample:After choosing the 2-member group, suppose the remaining 6 people are:
A, B, C, D, E, F
If we choose A, B, and C as the first 3-member group, then D, E, F automatically become the second 3-member group.
This gives:
- Group of 3: {A, B, C}
- Group of 3: {D, E, F}
But when we computed C(6,3), we also counted the case where we chose D, E, F first.
That gives:
- Group of 3: {D, E, F}
- Group of 3: {A, B, C}
These are not different divisions. The two 3-member groups have no labels such as "Group 1" and "Group 2". Swapping them does not create a new arrangement.
ExpertsGlobal5
In how many ways can a group of 8 people be divided into three groups, with 2, 3, and 3 members each?
A. 140
B. 280
C. 420
D. 560
E. 840
|
This Daily Butler Question was provided by
Experts' Global
|
|
Sponsored
|
|
|