Numbers Finder Using Geometric and Arithmetic Means

Input the geometric mean and arithmetic mean of two numbers to calculate the numbers themselves.

Calculate Two Numbers Using Geometric and Arithmetic Means

Result

How to Calculate Numbers Using Geometric and Arithmetic Means

Let the two numbers be \(x\) and \(y\), and their known values are:

Geometric Mean (\(G\)): The square root of the product of the two numbers: \( \text{Geometric Mean} = \sqrt{x \cdot y} \)

Arithmetic Mean (\(A\)): Half the sum of the two numbers: \( \text{Arithmetic Mean} = \frac{x + y}{2} \)

Using the geometric mean, calculate the product of the two numbers: \( x \cdot y = G^2 \) Using the arithmetic mean, calculate the sum of the two numbers: \( x + y = 2A \) Substituting the product and sum into a quadratic equation: \( t^2 - (2A)t + G^2 = 0 \) Use the quadratic formula to find \(t\): \( t = \frac{2A \pm \sqrt{(2A)^2 - 4 \cdot G^2}}{2} \) The two solutions correspond to \(x\) and \(y\).

Examples

Example 1: The geometric mean of two numbers is 8 and their arithmetic mean is 17, find the two number.

Solution:

1. Calculate the Product \( x \cdot y \):

\( x \cdot y = 8^2 = 64 \)

2. Calculate the Sum \( x + y \):

\( x + y = 2 \times 17 = 34 \)

3. Quadratic Equation:

\( t^2 - 34t + 64 = 0 \)

4. Solve the Equation:

\( t = \frac{34 \pm \sqrt{34^2 - 4 \cdot 64}}{2} = \frac{34 \pm \sqrt{1156 - 256}}{2} = \frac{34 \pm \sqrt{900}}{2} \)

\( t = \frac{34 \pm 30}{2} \)

\( t_1 = \frac{34 + 30}{2} = 32 \)

\( t_2 = \frac{34 - 30}{2} = 2 \)

Result: The two numbers are 32 and 2.

Example 2: Find two numbers whose geometric mean is 24 and arithmetic mean is 30.

Solution:

1. Calculate the Product \( x \cdot y \):

\( x \cdot y = 24^2 = 576 \)

2. Calculate the Sum \( x + y \):

\( x + y = 2 \times 30 = 60 \)

3. Quadratic Equation:

\( t^2 - 60t + 576 = 0 \)

4. Solve the Equation:

\( t = \frac{60 \pm \sqrt{60^2 - 4 \cdot 576}}{2} = \frac{60 \pm \sqrt{3600 - 2304}}{2} = \frac{60 \pm \sqrt{1296}}{2} \)

\( t = \frac{60 \pm 36}{2} \)

\( t_1 = \frac{60 + 36}{2} = 48 \)

\( t_2 = \frac{60 - 36}{2} = 12 \)

Result: The two numbers are 48 are 12.