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The variable [tex]$f$[/tex] varies inversely as the square root of [tex]$g$[/tex]. When [tex][tex]$f=4$[/tex][/tex] and [tex]$g=4$[/tex], Jordan's work finding the value of [tex]$f$[/tex] when [tex][tex]$g=100$[/tex][/tex] is shown below:

[tex]\[
\begin{array}{l}
f \sqrt{g}=k \\
4 \sqrt{4} = k \\
4 \cdot 2 = k \\
8 = k \\
f \sqrt{g} = 8 \\
f \sqrt{100} = 8 \\
f \cdot 10 = 8 \\
f = \frac{8}{10} \\
f = 0.8
\end{array}
\][/tex]

What is the first error, if any, in Jordan's work?

A. He used an equation that models direct variation instead of inverse variation.
B. He substituted incorrectly when calculating the constant of variation.
C. He took the square root of the wrong variable.
D. He did not make any errors.

Sagot :

To solve this problem, we need to understand that the variable [tex]\( f \)[/tex] varies inversely as the square root of [tex]\( g \)[/tex]. This relationship can be expressed by the equation:

[tex]\[ f = \frac{k}{\sqrt{g}} \][/tex]

Here, [tex]\( k \)[/tex] is the constant of variation.

First, let's find the correct constant of variation using the provided values [tex]\( f = 4 \)[/tex] and [tex]\( g = 4 \)[/tex]:

[tex]\[ f = \frac{k}{\sqrt{g}} \][/tex]

Substituting the given values:

[tex]\[ 4 = \frac{k}{\sqrt{4}} \][/tex]

Since [tex]\( \sqrt{4} = 2 \)[/tex]:

[tex]\[ 4 = \frac{k}{2} \][/tex]

Solving for [tex]\( k \)[/tex]:

[tex]\[ k = 4 \times 2 \][/tex]
[tex]\[ k = 8 \][/tex]

Now, let's find the value of [tex]\( f \)[/tex] when [tex]\( g = 100 \)[/tex]:

[tex]\[ f = \frac{8}{\sqrt{100}} \][/tex]

Since [tex]\( \sqrt{100} = 10 \)[/tex]:

[tex]\[ f = \frac{8}{10} \][/tex]
[tex]\[ f = 0.8 \][/tex]

By examining Jordar's work:
[tex]\[ \begin{array}{l} t \sqrt{g}=k \\ 4(4)=k \\ 16=k \\ I \sqrt{g}=16 \\ I \sqrt{100}=16 \\ 10 r=16 \\ I=16 \end{array} \][/tex]

We see the first error is in the very first step. Jordar used the equation [tex]\( t \sqrt{g} = k \)[/tex], which models a direct variation instead of an inverse variation.

Therefore, the first error in Jordar's work is:

A. He used an equation that models direct variation instead of inverse variation.