Math Problem Statement

The first term of a geometric sequence is \( \frac{2}{3} \). The next three terms are \( \frac{1}{2} \), \( \frac{3}{8} \), and \( \frac{9}{32} \). What is the tenth term of the sequence?

Solution

To find the tenth term of the given geometric sequence, we can use the general formula for the nn-th term of a geometric sequence: an=arn1a_n = a \cdot r^{n-1} where:

  • aa is the first term of the sequence,
  • rr is the common ratio, and
  • nn is the term number.

Step-by-Step Solution

  1. Identify the First Term (aa): The first term aa is given as 23\frac{2}{3}.

  2. Determine the Common Ratio (rr): To find the common ratio, divide the second term by the first term: r=1223=1232=34r = \frac{\frac{1}{2}}{\frac{2}{3}} = \frac{1}{2} \cdot \frac{3}{2} = \frac{3}{4} So, the common ratio rr is 34\frac{3}{4}.

  3. Find the Tenth Term (a10a_{10}): Substitute a=23a = \frac{2}{3}, r=34r = \frac{3}{4}, and n=10n = 10 into the formula: a10=23(34)101a_{10} = \frac{2}{3} \cdot \left( \frac{3}{4} \right)^{10-1} =23(34)9= \frac{2}{3} \cdot \left( \frac{3}{4} \right)^9

  4. Calculate (34)9\left( \frac{3}{4} \right)^9 and Multiply: To find the exact value, you can compute (34)9\left( \frac{3}{4} \right)^9 and then multiply by 23\frac{2}{3}, or approximate it using a calculator.

However, expressing a10a_{10} as: a10=23(34)9a_{10} = \frac{2}{3} \cdot \left( \frac{3}{4} \right)^9 is often sufficient in exact form unless further simplification or a decimal approximation is needed.

Would you like the decimal approximation for the value or more details on any steps?

Here are some related questions:

  1. How would the sequence behave if the common ratio was greater than 1?
  2. What would the 15th term be in this sequence?
  3. How do you determine the sum of the first nn terms of a geometric sequence?
  4. How does the common ratio affect whether the sequence converges or diverges?
  5. What is the limit of the terms of the sequence as nn \to \infty in this case?

Tip: In geometric sequences, a common ratio between 0 and 1 leads to terms that decrease in magnitude, while a ratio greater than 1 increases the magnitude of terms.

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Math Problem Analysis

Mathematical Concepts

Geometric Sequence
Exponential Growth
Common Ratio

Formulas

\( a_n = a \cdot r^{n-1} \)

Theorems

Geometric Sequence Formula

Suitable Grade Level

Grades 9-11