Chapter 6: Problem 34
Find three geometric means between 3 and 9\(\frac{13}{27}\) .
Short Answer
Expert verified
The three geometric means are found using the common ratio \(r = \sqrt[4]{\frac{244}{81}}\): calculate \(G_1 = 3r\), \(G_2 = 3r^2\), \(G_3 = 3r^3\).
Step by step solution
01
Understand the Problem
To find three geometric means between two numbers, we are essentially looking for four numbers forming a geometric sequence: the first number, the three means, and the last number. A geometric sequence is a set of numbers where each term after the first is found by multiplying the previous term by a constant called the common ratio.
02
Setup the Geometric Sequence
Let's denote the terms of the sequence as: 3, \(G_1\), \(G_2\), \(G_3\), and \(9\frac{13}{27}\) (the given fraction can also be written as \(\frac{244}{27}\)). We define the common ratio as \(r\), so the sequence can be expressed as: \(3, 3r, 3r^2, 3r^3, 3r^4 = 9\frac{13}{27}\).
03
Formulate the Equation for Common Ratio
Given the sequence, the equation we need to solve is: \(3r^4 = \frac{244}{27}\). Divide through by 3 to isolate \(r^4\): \(r^4 = \frac{244}{81}\).
04
Solve for the Common Ratio
Now we need to solve for \(r\) by taking the fourth root of both sides of the equation. Hence, \(r = \sqrt[4]{\frac{244}{81}}\). Use a calculator to find \(r\).
05
Calculate the Geometric Means
With the common ratio \(r\) determined, calculate the geometric means: \(G_1 = 3r\), \(G_2 = 3r^2\), \(G_3 = 3r^3\). These are the desired values of the three geometric means.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Common Ratio
In a geometric sequence, the term "common ratio" refers to the constant factor that you multiply each term by to get the next term. This ratio plays a crucial role in defining the sequence. For instance, consider a simple example: if you have a sequence starting with 2, 6, 18, and so on, the common ratio here is 3 because you multiply each term by 3 to get the next term.
- To find the common ratio, you can divide any term in the sequence by its preceding term.
- Mathematically, the formula to calculate the common ratio \( r \) from terms \( a_n \) and \( a_{n-1} \) is: \[ r = \frac{a_n}{a_{n-1}} \]
Geometric Means
Geometric means fill the values in a geometric sequence between two numbers, maintaining the common ratio. When you say you're looking for geometric means, it means you need to find intermediate values in such a sequence. Suppose you're bridging two known numbers in a geometric sequence like 3 and 81.
- For example, if you find one geometric mean between 3 and 27, it makes the sequence: 3, 9, 27. Here, 9 is the geometric mean because it continues the progression.
- To find multiple geometric means, assume terms between the starting and ending values, and apply the common ratio to solve for them.
Fourth Root
Taking a fourth root is a mathematical operation involving finding a number which, when raised to the power of four, equals the original number. In simpler terms, it reverses the process of raising to the power of four.
- For example, if you have \( x^4 = 81 \), then \( x = \sqrt[4]{81} = 3 \), because \( 3^4 = 81 \).
- Calculating a fourth root is usually straightforward with a calculator, crucial in determining the common ratio here.