Math Problem Statement

​The first term of a geometric sequence is 2/3. The next three terms are 1/2, 3/8, and 9/32. What is the tenth term of the sequence?

Solution

In a geometric sequence, each term is obtained by multiplying the previous term by a common ratio, rr. Given the terms:

  • First term (aa) = 23\frac{2}{3}
  • Second term = 12\frac{1}{2}
  • Third term = 38\frac{3}{8}
  • Fourth term = 932\frac{9}{32}

Step 1: Finding the Common Ratio, rr

To find the common ratio, divide the second term by the first term: r=1223=12×32=34r = \frac{\frac{1}{2}}{\frac{2}{3}} = \frac{1}{2} \times \frac{3}{2} = \frac{3}{4}

To verify, check the ratio for the third and fourth terms: r=3812=38×2=34r = \frac{\frac{3}{8}}{\frac{1}{2}} = \frac{3}{8} \times 2 = \frac{3}{4} r=93238=932×83=34r = \frac{\frac{9}{32}}{\frac{3}{8}} = \frac{9}{32} \times \frac{8}{3} = \frac{3}{4}

So, the common ratio r=34r = \frac{3}{4} is consistent.

Step 2: Finding the Tenth Term

The nn-th term of a geometric sequence is given by: an=arn1a_n = a \cdot r^{n-1} For the tenth term (a10a_{10}): a10=23(34)9a_{10} = \frac{2}{3} \cdot \left( \frac{3}{4} \right)^{9}

Step 3: Calculating (34)9\left( \frac{3}{4} \right)^9

Calculating (34)9\left( \frac{3}{4} \right)^9 gives: (34)9=19683262144\left( \frac{3}{4} \right)^9 = \frac{19683}{262144}

Thus: a10=2319683262144=39366786432a_{10} = \frac{2}{3} \cdot \frac{19683}{262144} = \frac{39366}{786432}

After simplifying, we get: a10=19683393216a_{10} = \frac{19683}{393216}

So, the tenth term of the sequence is 19683393216\frac{19683}{393216}.

Would you like further details or have any questions?

Related Questions

  1. How do you find the common ratio in a geometric sequence?
  2. How can you determine if a sequence is geometric?
  3. What is the formula for the nn-th term of a geometric sequence?
  4. How do you calculate higher powers of fractions accurately?
  5. How can the sum of a geometric sequence be calculated?

Tip: When calculating terms in a geometric sequence, always verify the common ratio across multiple terms to ensure consistency.

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Math Problem Analysis

Mathematical Concepts

Algebra
Geometric Sequences

Formulas

nth term of a geometric sequence: a_n = a * r^(n-1)
Common ratio: r = a_(n+1) / a_n

Theorems

Properties of geometric sequences

Suitable Grade Level

Grades 9-12