Math Problem Statement

Find 3 geometric means between 256 and 1

Solution

To find 3 geometric means between 256 and 1, you can use the formula for the geometric sequence:

an=a1rn1a_n = a_1 \cdot r^{n-1}

Where:

  • ana_n is the nn-th term,
  • a1a_1 is the first term (256),
  • rr is the common ratio,
  • nn is the position of the term.

We need to find 3 geometric means, which implies that there are 5 terms in total: a1=256a_1 = 256, then 3 geometric means, and a5=1a_5 = 1.

The formula for the last term of a geometric sequence can be written as:

a5=a1r4a_5 = a_1 \cdot r^4

Substituting the known values:

1=256r41 = 256 \cdot r^4

Solve for r4r^4:

r4=1256r^4 = \frac{1}{256}

r4=2561=(28)1=28r^4 = 256^{-1} = (2^8)^{-1} = 2^{-8}

r=(28)14=22=14r = \left(2^{-8}\right)^{\frac{1}{4}} = 2^{-2} = \frac{1}{4}

So, the common ratio r=14r = \frac{1}{4}.

Now, we can find the geometric means. The sequence is:

a1=256,a2=256×14,a3=a2×14,a4=a3×14,a5=1a_1 = 256, \quad a_2 = 256 \times \frac{1}{4}, \quad a_3 = a_2 \times \frac{1}{4}, \quad a_4 = a_3 \times \frac{1}{4}, \quad a_5 = 1

Let's calculate these terms:

  1. a2=256×14=64a_2 = 256 \times \frac{1}{4} = 64,
  2. a3=64×14=16a_3 = 64 \times \frac{1}{4} = 16,
  3. a4=16×14=4a_4 = 16 \times \frac{1}{4} = 4.

Thus, the 3 geometric means between 256 and 1 are 64, 16, and 4.

Would you like further details on this method or have any questions?

Here are some related questions to deepen your understanding:

  1. What is the general formula for finding geometric means between two numbers?
  2. How do you determine the common ratio in a geometric sequence?
  3. How does a geometric sequence differ from an arithmetic sequence?
  4. What happens if you change the number of geometric means you want to find between two numbers?
  5. Can you apply this method to find geometric means between any two numbers?

Tip: The geometric mean of two numbers aa and bb can also be found as ab\sqrt{a \cdot b}.

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Math Problem Analysis

Mathematical Concepts

Geometric Sequences
Geometric Means

Formulas

Geometric sequence formula: a_n = a_1 * r^(n-1)
Common ratio calculation: r = (a_n / a_1)^(1/(n-1))

Theorems

Geometric sequence properties

Suitable Grade Level

Grades 8-10