Math Problem Statement

Find the 5th term of the geometric sequence where (a1=7) and the common ratio (r= 1/2)

Solution

To find the 5th term of a geometric sequence, you can use the formula:

an=a1×r(n1)a_n = a_1 \times r^{(n-1)}

Where:

  • ana_n is the nth term.
  • a1a_1 is the first term.
  • rr is the common ratio.
  • nn is the term number.

Given:

  • a1=7a_1 = 7
  • r=12r = \frac{1}{2}
  • n=5n = 5

Now, substitute these values into the formula:

a5=7×(12)(51)=7×(12)4a_5 = 7 \times \left(\frac{1}{2}\right)^{(5-1)} = 7 \times \left(\frac{1}{2}\right)^4

Calculate (12)4\left(\frac{1}{2}\right)^4:

(12)4=116\left(\frac{1}{2}\right)^4 = \frac{1}{16}

Now, multiply by 7:

a5=7×116=716a_5 = 7 \times \frac{1}{16} = \frac{7}{16}

So, the 5th term of the sequence is 716\frac{7}{16}.

Would you like more details or have any questions?


Here are five related questions:

  1. How do you find the sum of the first 5 terms in this geometric sequence?
  2. What would be the 8th term in this sequence?
  3. If the common ratio were 13\frac{1}{3} instead, what would the 5th term be?
  4. How does the common ratio affect the sequence as nn increases?
  5. Can you determine the 5th term if the first term and the common ratio were unknown but two other terms were provided?

Tip: When dealing with geometric sequences, always ensure the common ratio is correctly applied, especially with fractions or negative numbers.

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Math Problem Analysis

Mathematical Concepts

Geometric Sequences

Formulas

Geometric sequence nth term formula

Theorems

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Suitable Grade Level

Grades 9-12