If [tex]$y$[/tex] varies directly as [tex]$x$[/tex], and [tex]$y$[/tex] is 6 when [tex]$x$[/tex] is 72, what is the value of [tex]$y$[/tex] when [tex]$x$[/tex] is [tex]$8$[/tex]?

A. [tex]$\frac{1}{9}$[/tex]
B. [tex]$\frac{2}{3}$[/tex]
C. 54
D. 96



Answer :

To solve this problem, we need to understand the concept of direct variation. In a direct variation, the relationship between two variables [tex]\(x\)[/tex] and [tex]\(y\)[/tex] can be written as:

[tex]\[ y = kx \][/tex]

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

### Step-by-Step Solution

1. Identify the given values:
- When [tex]\( x = 72 \)[/tex], [tex]\( y = 6 \)[/tex].

2. Find the constant of variation [tex]\( k \)[/tex]:
Substitute the known values into the direct variation formula:

[tex]\[ 6 = k \cdot 72 \][/tex]

To isolate [tex]\( k \)[/tex], divide both sides by 72:

[tex]\[ k = \frac{6}{72} \][/tex]

Simplify the fraction:

[tex]\[ k = \frac{1}{12} \][/tex]

3. Use the constant [tex]\( k \)[/tex] to find [tex]\( y \)[/tex] when [tex]\( x = 8 \)[/tex]:
Substitute [tex]\( k = \frac{1}{12} \)[/tex] and [tex]\( x = 8 \)[/tex] back into the direct variation formula:

[tex]\[ y = \frac{1}{12} \cdot 8 \][/tex]

Simplify the multiplication:

[tex]\[ y = \frac{8}{12} \][/tex]

Further simplify the fraction:

[tex]\[ y = \frac{2}{3} \][/tex]

Therefore, the value of [tex]\( y \)[/tex] when [tex]\( x = 8 \)[/tex] is [tex]\( \frac{2}{3} \)[/tex].

The correct answer is [tex]\( \boxed{\frac{2}{3}} \)[/tex].