Math Problem Statement

Melisa memiliki 7 buah manik besar beraneka warna dan 7 buah manik kecil beraneka warna yang akan ia susun menjadi sebuah gelang. Tentukan banyaknya susunan manik yang akan ia miliki apabila: a) Tidak ada syarat apapun b) Manik besar dan kecil harus disusun berselang seling

Solution

The problem in the image is related to counting the number of different ways of arranging beads on a bracelet, with certain constraints.

Problem Breakdown:

Melisa has 7 large beads, each of different colors, and 7 small beads, each of different colors. She will arrange them in a bracelet. You are tasked with finding the number of possible arrangements under the following conditions:

a) No conditions (no restrictions). b) The large and small beads must alternate.


Let's begin by solving each case:

a) No restrictions on the arrangement:

Since it's a bracelet, we need to account for the fact that it can be rotated and reflected (i.e., the arrangement is the same even if it's rotated or flipped).

  • Number of arrangements without any restrictions:

There are 14 beads in total (7 large and 7 small), and in a circular arrangement, fixing one bead in place eliminates identical arrangements caused by rotation. After fixing one bead, the remaining beads can be arranged in any order.

Thus, the total number of ways to arrange the beads is:

(141)!2\frac{(14-1)!}{2}

The factor of 12\frac{1}{2} accounts for reflection (flipping the bracelet).


b) The large and small beads must alternate:

Here, the large beads and small beads must alternate. This significantly restricts the arrangements because we must alternate between large and small beads.

  • First, we can fix one large bead in place (since it's a circular arrangement), and then arrange the 6 remaining large beads in any order.

  • Similarly, the 7 small beads can be arranged in any order in the remaining spots.

Thus, the total number of ways to arrange the beads, given that they alternate, is:

7!×7!2\frac{7! \times 7!}{2}

This accounts for the alternating placement of large and small beads, with the factor 12\frac{1}{2} to account for reflection.


Would you like more details on the calculations, or is there anything else you'd like me to clarify?

Additional questions:

  1. How would the arrangement change if the beads were all of the same color?
  2. What happens if the beads are arranged in a linear, rather than circular, fashion?
  3. How can symmetry and group theory be used to solve this problem in a more general sense?
  4. If some beads are indistinguishable, how would that affect the count of arrangements?
  5. Can you think of any other arrangements (such as grouping colors) that would affect the total number?

Tip: When dealing with circular arrangements, remember to account for rotational and reflective symmetries to avoid overcounting!

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Math Problem Analysis

Mathematical Concepts

Permutations
Circular Arrangements
Factorials

Formulas

n! for permutations of n items
(n-1)! for circular permutations
(n-1)! / 2 for circular permutations with reflection

Theorems

Circular Permutation Theorem
Factorial Properties

Suitable Grade Level

Grades 10-12