Questions: Barb is making a bead necklace. She strings 1 white bead, then 3 blue beads, then 1 white bead, and so on. Write the numbers for the first eight beads that are white. What is a rule for the pattern?
Transcript text: Barb is making a bead necklace. She strings 1 white bead, then 3 blue beads, then 1 white bead, and so on. Write the numbers for the first eight beads that are white. What is a rule for the pattern?
Solution
Solution Steps
Step 1: Analyze the pattern
Barb strings beads in the following repeating sequence: 1 white bead, followed by 3 blue beads. This pattern repeats continuously. The sequence of beads can be represented as:
\[
\text{White}, \text{Blue}, \text{Blue}, \text{Blue}, \text{White}, \text{Blue}, \text{Blue}, \text{Blue}, \dots
\]
Step 2: Identify the positions of white beads
The white beads appear at the beginning of each repetition of the pattern. The positions of the first eight white beads are:
Position 1 (1st bead)
Position 5 (5th bead)
Position 9 (9th bead)
Position 13 (13th bead)
Position 17 (17th bead)
Position 21 (21st bead)
Position 25 (25th bead)
Position 29 (29th bead)
Step 3: Derive the rule for the pattern
The positions of the white beads follow an arithmetic sequence where each white bead is 4 positions apart. The rule for the \(n\)-th white bead's position is:
\[
\text{Position of } n\text{-th white bead} = 4n - 3
\]
Final Answer
The positions of the first eight white beads are:
\[
\boxed{1, 5, 9, 13, 17, 21, 25, 29}
\]
The rule for the pattern is:
\[
\boxed{\text{Position of } n\text{-th white bead} = 4n - 3}
\]